81750921 has 32 divisors (see below), whose sum is σ = 127948800. Its totient is φ = 45467136.

The previous prime is 81750899. The next prime is 81750941. The reversal of 81750921 is 12905718.

It is not a de Polignac number, because 81750921 - 2⁷ = 81750793 is a prime.

It is not an unprimeable number, because it can be changed into a prime (81750941) by changing a digit.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 136180 + ... + 136778.

It is an arithmetic number, because the mean of its divisors is an integer number (3998400).

Almost surely, 2^81750921 is an apocalyptic number.

It is an amenable number.

81750921 is a deficient number, since it is larger than the sum of its proper divisors (46197879).

81750921 is a wasteful number, since it uses less digits than its factorization.

81750921 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 773.

The product of its (nonzero) digits is 5040, while the sum is 33.

The square root of 81750921 is about 9041.6215912855. The cubic root of 81750921 is about 434.0078166176.

The spelling of 81750921 in words is "eighty-one million, seven hundred fifty thousand, nine hundred twenty-one".