81921432 has 32 divisors (see below), whose sum is σ = 205044480. Its totient is φ = 27275040.

The previous prime is 81921431. The next prime is 81921439. The reversal of 81921432 is 23412918.

It is a super-2 number, since 2×81921432² = 13422242041861248, 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 81921432.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81921431) 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, 27957 + ... + 30747.

It is an arithmetic number, because the mean of its divisors is an integer number (6407640).

Almost surely, 2^81921432 is an apocalyptic number.

It is an amenable number.

81921432 is an abundant number, since it is smaller than the sum of its proper divisors (123123048).

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

81921432 is a wasteful number, since it uses less digits than its factorization.

81921432 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4023 (or 4019 counting only the distinct ones).

The product of its digits is 3456, while the sum is 30.

The square root of 81921432 is about 9051.0459064132. The cubic root of 81921432 is about 434.3093492694.

The spelling of 81921432 in words is "eighty-one million, nine hundred twenty-one thousand, four hundred thirty-two".