21351423397 has 2 divisors, whose sum is σ = 21351423398. Its totient is φ = 21351423396.

The previous prime is 21351423371. The next prime is 21351423481. The reversal of 21351423397 is 79332415312.

It is a happy number.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 12723614401 + 8627808996 = 112799^2 + 92886^2 .

It is a cyclic number.

It is not a de Polignac number, because 21351423397 - 2²³ = 21343034789 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21351423367) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10675711698 + 10675711699.

It is an arithmetic number, because the mean of its divisors is an integer number (10675711699).

Almost surely, 2^21351423397 is an apocalyptic number.

It is an amenable number.

21351423397 is a deficient number, since it is larger than the sum of its proper divisors (1).

21351423397 is an equidigital number, since it uses as much as digits as its factorization.

21351423397 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 136080, while the sum is 40.

The spelling of 21351423397 in words is "twenty-one billion, three hundred fifty-one million, four hundred twenty-three thousand, three hundred ninety-seven".