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81000000 = 263456

81000000 has 245 divisors, whose sum is σ = 300132877. Its totient is φ = 21600000.

The previous prime is 80999957. The next prime is 81000001. The reversal of 81000000 is 18.

Adding to 81000000 its reverse (18), we get a palindrome (81000018).

The square root of 81000000 is 9000.

It is a perfect power (a square), and thus also a powerful number.

It can be written as a sum of positive squares in 3 ways, for example, as 70963776 + 10036224 = 8424^2 + 3168^2 .

It is an ABA number since it can be written as A⋅BA, here for A=3, B=300.

It is a super-2 number, since 2×810000002 = 13122000000000000, which contains 22 as substring.

It is a Harshad number since it is a multiple of its sum of digits (9).

It is a super Niven number, because it is divisible the sum of any subset of its (nonzero) digits.

It is a Duffinian number.

It is a nialpdrome in base 10.

It is not an unprimeable number, because it can be changed into a prime (81000001) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 34 ways as a sum of consecutive naturals, for example, 16199998 + ... + 16200002.

Almost surely, 281000000 is an apocalyptic number.

81000000 is a gapful number since it is divisible by the number (80) formed by its first and last digit.

81000000 is the 9000-th square number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 81000000

81000000 is an abundant number, since it is smaller than the sum of its proper divisors (219132877).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

81000000 is an frugal number, since it uses more digits than its factorization.

81000000 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 54 (or 10 counting only the distinct ones).

The product of its (nonzero) digits is 8, while the sum is 9.

The cubic root of 81000000 is about 432.6748710922.

The spelling of 81000000 in words is "eighty-one million", and thus it is an aban number and an uban number.