81939100 has 18 divisors (see below), whose sum is σ = 177808064. Its totient is φ = 32775600.

The previous prime is 81939089. The next prime is 81939103. The reversal of 81939100 is 193918.

It is a super-2 number, since 2×81939100² = 13428032217620000, which contains 22 as substring.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81939103) by changing a digit.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 409596 + ... + 409795.

Almost surely, 2^81939100 is an apocalyptic number.

It is an amenable number.

81939100 is an abundant number, since it is smaller than the sum of its proper divisors (95868964).

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

81939100 is a wasteful number, since it uses less digits than its factorization.

81939100 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 819405 (or 819398 counting only the distinct ones).

The product of its (nonzero) digits is 1944, while the sum is 31.

The square root of 81939100 is about 9052.0218735927. The cubic root of 81939100 is about 434.3405695326.

The spelling of 81939100 in words is "eighty-one million, nine hundred thirty-nine thousand, one hundred".