721930991 has 2 divisors, whose sum is σ = 721930992. Its totient is φ = 721930990.

The previous prime is 721930943. The next prime is 721931009. The reversal of 721930991 is 199039127.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 721930991 - 2⁶ = 721930927 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (721930921) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 360965495 + 360965496.

It is an arithmetic number, because the mean of its divisors is an integer number (360965496).

Almost surely, 2^721930991 is an apocalyptic number.

721930991 is a deficient number, since it is larger than the sum of its proper divisors (1).

721930991 is an equidigital number, since it uses as much as digits as its factorization.

721930991 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 30618, while the sum is 41.

The square root of 721930991 is about 26868.7735298804. The cubic root of 721930991 is about 897.0814889095.

The spelling of 721930991 in words is "seven hundred twenty-one million, nine hundred thirty thousand, nine hundred ninety-one".