81974920 has 32 divisors (see below), whose sum is σ = 184754520. Its totient is φ = 32734720.

The previous prime is 81974917. The next prime is 81974923. The reversal of 81974920 is 2947918.

It is an interprime number because it is at equal distance from previous prime (81974917) and next prime (81974923).

It can be written as a sum of positive squares in 4 ways, for example, as 33616804 + 48358116 = 5798^2 + 6954^2 .

It is a Harshad number since it is a multiple of its sum of digits (40).

It is not an unprimeable number, because it can be changed into a prime (81974923) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 29094 + ... + 31786.

Almost surely, 2^81974920 is an apocalyptic number.

It is an amenable number.

81974920 is an abundant number, since it is smaller than the sum of its proper divisors (102779600).

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

81974920 is a wasteful number, since it uses less digits than its factorization.

81974920 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3465 (or 3461 counting only the distinct ones).

The product of its (nonzero) digits is 36288, while the sum is 40.

The square root of 81974920 is about 9054.0002208968. Note that the first 3 decimals coincide. The cubic root of 81974920 is about 434.4038515419.

The spelling of 81974920 in words is "eighty-one million, nine hundred seventy-four thousand, nine hundred twenty".