81949900 has 18 divisors (see below), whose sum is σ = 177831500. Its totient is φ = 32779920.

The previous prime is 81949891. The next prime is 81949919. The reversal of 81949900 is 994918.

It is a super-2 number, since 2×81949900² = 13431572220020000, which contains 22 as substring.

It is an unprimeable number.

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, 409650 + ... + 409849.

Almost surely, 2^81949900 is an apocalyptic number.

It is an amenable number.

81949900 is an abundant number, since it is smaller than the sum of its proper divisors (95881600).

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

81949900 is a wasteful number, since it uses less digits than its factorization.

81949900 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 819513 (or 819506 counting only the distinct ones).

The product of its (nonzero) digits is 23328, while the sum is 40.

The square root of 81949900 is about 9052.6184057432. The cubic root of 81949900 is about 434.3596514771.

The spelling of 81949900 in words is "eighty-one million, nine hundred forty-nine thousand, nine hundred".