81000560 has 20 divisors (see below), whose sum is σ = 188326488. Its totient is φ = 32400192.

The previous prime is 81000541. The next prime is 81000571. The reversal of 81000560 is 6500018.

It is a tau number, because it is divible by the number of its divisors (20).

It is a super-2 number, since 2×81000560² = 13122181440627200, which contains 22 as substring.

It is a Harshad number since it is a multiple of its sum of digits (20).

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 506174 + ... + 506333.

Almost surely, 2^81000560 is an apocalyptic number.

81000560 is a gapful number since it is divisible by the number (80) formed by its first and last digit.

It is an amenable number.

81000560 is an abundant number, since it is smaller than the sum of its proper divisors (107325928).

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

81000560 is a wasteful number, since it uses less digits than its factorization.

81000560 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1012520 (or 1012514 counting only the distinct ones).

The product of its (nonzero) digits is 240, while the sum is 20.

The square root of 81000560 is about 9000.0311110573. The cubic root of 81000560 is about 432.6758682007.

Adding to 81000560 its reverse (6500018), we get a palindrome (87500578).

The spelling of 81000560 in words is "eighty-one million, five hundred sixty", and thus it is an aban number.