81161900 has 18 divisors (see below), whose sum is σ = 176121540. Its totient is φ = 32464720.

The previous prime is 81161891. The next prime is 81161929. The reversal of 81161900 is 916118.

It is a super-2 number, since 2×81161900² = 13174508023220000, which contains 22 as substring.

It is a self number, because there is not a number n which added to its sum of digits gives 81161900.

It is an unprimeable number.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 405710 + ... + 405909.

It is an arithmetic number, because the mean of its divisors is an integer number (9784530).

Almost surely, 2^81161900 is an apocalyptic number.

It is an amenable number.

81161900 is an abundant number, since it is smaller than the sum of its proper divisors (94959640).

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

81161900 is a wasteful number, since it uses less digits than its factorization.

81161900 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 811633 (or 811626 counting only the distinct ones).

The product of its (nonzero) digits is 432, while the sum is 26.

The square root of 81161900 is about 9008.9899544844. The cubic root of 81161900 is about 432.9629511012.

The spelling of 81161900 in words is "eighty-one million, one hundred sixty-one thousand, nine hundred".