819981921 has 32 divisors (see below), whose sum is σ = 1243579392. Its totient is φ = 476199360.

The previous prime is 819981871. The next prime is 819981937. The reversal of 819981921 is 129189918.

It is not a de Polignac number, because 819981921 - 2¹⁴ = 819965537 is a prime.

It is not an unprimeable number, because it can be changed into a prime (819981221) 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, 69756 + ... + 80658.

It is an arithmetic number, because the mean of its divisors is an integer number (38861856).

Almost surely, 2^819981921 is an apocalyptic number.

It is an amenable number.

819981921 is a deficient number, since it is larger than the sum of its proper divisors (423597471).

819981921 is a wasteful number, since it uses less digits than its factorization.

819981921 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 11013.

The product of its digits is 93312, while the sum is 48.

The square root of 819981921 is about 28635.3264517798. The cubic root of 819981921 is about 935.9832834968.

The spelling of 819981921 in words is "eight hundred nineteen million, nine hundred eighty-one thousand, nine hundred twenty-one".