21390993317 has 2 divisors, whose sum is σ = 21390993318. Its totient is φ = 21390993316.

The previous prime is 21390993289. The next prime is 21390993353. The reversal of 21390993317 is 71339909312.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 13829995201 + 7560998116 = 117601^2 + 86954^2 .

It is a cyclic number.

It is not a de Polignac number, because 21390993317 - 2²² = 21386799013 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21390993517) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10695496658 + 10695496659.

It is an arithmetic number, because the mean of its divisors is an integer number (10695496659).

Almost surely, 2^21390993317 is an apocalyptic number.

It is an amenable number.

21390993317 is a deficient number, since it is larger than the sum of its proper divisors (1).

21390993317 is an equidigital number, since it uses as much as digits as its factorization.

21390993317 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 275562, while the sum is 47.

The spelling of 21390993317 in words is "twenty-one billion, three hundred ninety million, nine hundred ninety-three thousand, three hundred seventeen".