81929780 has 12 divisors (see below), whose sum is σ = 172052580. Its totient is φ = 32771904.

The previous prime is 81929777. The next prime is 81929821. The reversal of 81929780 is 8792918.

It can be written as a sum of positive squares in 2 ways, for example, as 42667024 + 39262756 = 6532^2 + 6266^2 .

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 2048225 + ... + 2048264.

It is an arithmetic number, because the mean of its divisors is an integer number (14337715).

Almost surely, 2^81929780 is an apocalyptic number.

It is an amenable number.

81929780 is an abundant number, since it is smaller than the sum of its proper divisors (90122800).

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

81929780 is a wasteful number, since it uses less digits than its factorization.

81929780 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 4096498 (or 4096496 counting only the distinct ones).

The product of its (nonzero) digits is 72576, while the sum is 44.

The square root of 81929780 is about 9051.5070568387. The cubic root of 81929780 is about 434.3241011734.

The spelling of 81929780 in words is "eighty-one million, nine hundred twenty-nine thousand, seven hundred eighty".