21758647637 has 2 divisors, whose sum is σ = 21758647638. Its totient is φ = 21758647636.

The previous prime is 21758647627. The next prime is 21758647661. The reversal of 21758647637 is 73674685712.

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., 21062426641 + 696220996 = 145129^2 + 26386^2 .

It is a cyclic number.

It is not a de Polignac number, because 21758647637 - 2¹⁶ = 21758582101 is a prime.

It is a super-2 number, since 2×21758647637² (a number of 21 digits) contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21758647627) 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, 10879323818 + 10879323819.

It is an arithmetic number, because the mean of its divisors is an integer number (10879323819).

Almost surely, 2^21758647637 is an apocalyptic number.

It is an amenable number.

21758647637 is a deficient number, since it is larger than the sum of its proper divisors (1).

21758647637 is an equidigital number, since it uses as much as digits as its factorization.

21758647637 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 11854080, while the sum is 56.

The spelling of 21758647637 in words is "twenty-one billion, seven hundred fifty-eight million, six hundred forty-seven thousand, six hundred thirty-seven".