81936921 has 8 divisors (see below), whose sum is σ = 119181024. Its totient is φ = 49658720.

The previous prime is 81936917. The next prime is 81936929. The reversal of 81936921 is 12963918.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 81936921 - 2² = 81936917 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 81936921.

It is not an unprimeable number, because it can be changed into a prime (81936929) 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, 1241436 + ... + 1241501.

It is an arithmetic number, because the mean of its divisors is an integer number (14897628).

Almost surely, 2^81936921 is an apocalyptic number.

It is an amenable number.

81936921 is a deficient number, since it is larger than the sum of its proper divisors (37244103).

81936921 is a wasteful number, since it uses less digits than its factorization.

81936921 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2482951.

The product of its digits is 23328, while the sum is 39.

The square root of 81936921 is about 9051.9015129419. The cubic root of 81936921 is about 434.3367193703.

The spelling of 81936921 in words is "eighty-one million, nine hundred thirty-six thousand, nine hundred twenty-one".