21937614781 has 2 divisors, whose sum is σ = 21937614782. Its totient is φ = 21937614780.

The previous prime is 21937614773. The next prime is 21937614817. The reversal of 21937614781 is 18741673912.

Together with next prime (21937614817) it forms an Ormiston pair, because they use the same digits, order apart.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 21878847225 + 58767556 = 147915^2 + 7666^2 .

It is a cyclic number.

It is not a de Polignac number, because 21937614781 - 2³ = 21937614773 is a prime.

It is a super-2 number, since 2×21937614781² (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 (21937614701) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10968807390 + 10968807391.

It is an arithmetic number, because the mean of its divisors is an integer number (10968807391).

Almost surely, 2^21937614781 is an apocalyptic number.

It is an amenable number.

21937614781 is a deficient number, since it is larger than the sum of its proper divisors (1).

21937614781 is an equidigital number, since it uses as much as digits as its factorization.

21937614781 is an evil number, because the sum of its binary digits is even.

The product of its digits is 508032, while the sum is 49.

The spelling of 21937614781 in words is "twenty-one billion, nine hundred thirty-seven million, six hundred fourteen thousand, seven hundred eighty-one".