81330921 has 72 divisors (see below), whose sum is σ = 147498624. Its totient is φ = 42197760.

The previous prime is 81330863. The next prime is 81330923. The reversal of 81330921 is 12903318.

It is not a de Polignac number, because 81330921 - 2⁶ = 81330857 is a prime.

It is a super-2 number, since 2×81330921² = 13229437421416482, which contains 22 as substring.

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (81330923) by changing a digit.

It is a polite number, since it can be written in 71 ways as a sum of consecutive naturals, for example, 1983661 + ... + 1983701.

It is an arithmetic number, because the mean of its divisors is an integer number (2048592).

Almost surely, 2^81330921 is an apocalyptic number.

It is an amenable number.

81330921 is a deficient number, since it is larger than the sum of its proper divisors (66167703).

81330921 is a wasteful number, since it uses less digits than its factorization.

81330921 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 151 (or 111 counting only the distinct ones).

The product of its (nonzero) digits is 1296, while the sum is 27.

The square root of 81330921 is about 9018.3657610456. The cubic root of 81330921 is about 433.2632935453.

The spelling of 81330921 in words is "eighty-one million, three hundred thirty thousand, nine hundred twenty-one".