999921931 has 2 divisors, whose sum is σ = 999921932. Its totient is φ = 999921930.

The previous prime is 999921907. The next prime is 999921947. The reversal of 999921931 is 139129999.

It is a strong prime.

It is an emirp because it is prime and its reverse (139129999) is a distict prime.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-999921931 is a prime.

It is a super-2 number, since 2×999921931² = 1999687736189537522, which contains 22 as substring.

It is not a weakly prime, because it can be changed into another prime (999921331) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 499960965 + 499960966.

It is an arithmetic number, because the mean of its divisors is an integer number (499960966).

Almost surely, 2^999921931 is an apocalyptic number.

999921931 is a deficient number, since it is larger than the sum of its proper divisors (1).

999921931 is an equidigital number, since it uses as much as digits as its factorization.

999921931 is an evil number, because the sum of its binary digits is even.

The product of its digits is 354294, while the sum is 52.

The square root of 999921931 is about 31621.5421983179. The cubic root of 999921931 is about 999.9739763228.

The spelling of 999921931 in words is "nine hundred ninety-nine million, nine hundred twenty-one thousand, nine hundred thirty-one".