81238100 has 18 divisors (see below), whose sum is σ = 176286894. Its totient is φ = 32495200.

The previous prime is 81238099. The next prime is 81238109. The reversal of 81238100 is 183218.

It can be written as a sum of positive squares in 3 ways, for example, as 633616 + 80604484 = 796^2 + 8978^2 .

It is a super-2 number, since 2×81238100² = 13199257783220000, which contains 22 as substring.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81238109) 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 5 ways as a sum of consecutive naturals, for example, 406091 + ... + 406290.

Almost surely, 2^81238100 is an apocalyptic number.

It is an amenable number.

81238100 is an abundant number, since it is smaller than the sum of its proper divisors (95048794).

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

81238100 is a wasteful number, since it uses less digits than its factorization.

81238100 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 812395 (or 812388 counting only the distinct ones).

The product of its (nonzero) digits is 384, while the sum is 23.

The square root of 81238100 is about 9013.2180712551. The cubic root of 81238100 is about 433.0984065194.

The spelling of 81238100 in words is "eighty-one million, two hundred thirty-eight thousand, one hundred".