81921812 has 12 divisors (see below), whose sum is σ = 163843680. Its totient is φ = 35109336.

The previous prime is 81921797. The next prime is 81921857. The reversal of 81921812 is 21812918.

81921812 is an admirable number.

It is a super-2 number, since 2×81921812² = 13422366562726688, which contains 22 as substring.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 1462862 + ... + 1462917.

It is an arithmetic number, because the mean of its divisors is an integer number (13653640).

Almost surely, 2^81921812 is an apocalyptic number.

It is an amenable number.

81921812 is a primitive abundant number, since it is smaller than the sum of its proper divisors, none of which is abundant.

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

81921812 is a wasteful number, since it uses less digits than its factorization.

81921812 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2925790 (or 2925788 counting only the distinct ones).

The product of its digits is 2304, while the sum is 32.

The square root of 81921812 is about 9051.0668984380. The cubic root of 81921812 is about 434.3100207961.

The spelling of 81921812 in words is "eighty-one million, nine hundred twenty-one thousand, eight hundred twelve".