21391358837 has 2 divisors, whose sum is σ = 21391358838. Its totient is φ = 21391358836.

The previous prime is 21391358809. The next prime is 21391358839. The reversal of 21391358837 is 73885319312.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 17211865636 + 4179493201 = 131194^2 + 64649^2 .

It is a cyclic number.

It is not a de Polignac number, because 21391358837 - 2¹⁸ = 21391096693 is a prime.

Together with 21391358839, it forms a pair of twin primes.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21391358839) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10695679418 + 10695679419.

It is an arithmetic number, because the mean of its divisors is an integer number (10695679419).

Almost surely, 2^21391358837 is an apocalyptic number.

It is an amenable number.

21391358837 is a deficient number, since it is larger than the sum of its proper divisors (1).

21391358837 is an equidigital number, since it uses as much as digits as its factorization.

21391358837 is an evil number, because the sum of its binary digits is even.

The product of its digits is 1088640, while the sum is 50.

The spelling of 21391358837 in words is "twenty-one billion, three hundred ninety-one million, three hundred fifty-eight thousand, eight hundred thirty-seven".