81163638 has 24 divisors (see below), whose sum is σ = 176023848. Its totient is φ = 27028512.

The previous prime is 81163633. The next prime is 81163697. The reversal of 81163638 is 83636118.

81163638 is a `hidden beast` number, since 8 + 1 + 16 + 3 + 638 = 666.

It is a super-2 number, since 2×81163638² = 13175072266790088, which contains 22 as substring.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81163633) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 29706 + ... + 32322.

It is an arithmetic number, because the mean of its divisors is an integer number (7334327).

Almost surely, 2^81163638 is an apocalyptic number.

81163638 is an abundant number, since it is smaller than the sum of its proper divisors (94860210).

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

81163638 is a wasteful number, since it uses less digits than its factorization.

81163638 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4348 (or 4345 counting only the distinct ones).

The product of its digits is 20736, while the sum is 36.

The square root of 81163638 is about 9009.0864131720. The cubic root of 81163638 is about 432.9660415670.

The spelling of 81163638 in words is "eighty-one million, one hundred sixty-three thousand, six hundred thirty-eight".