21373660666591 has 2 divisors, whose sum is σ = 21373660666592. Its totient is φ = 21373660666590.

The previous prime is 21373660666513. The next prime is 21373660666597. The reversal of 21373660666591 is 19566606637312.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 21373660666591 - 2²³ = 21373652277983 is a prime.

It is a super-2 number, since 2×21373660666591² (a number of 27 digits) contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21373660666597) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10686830333295 + 10686830333296.

It is an arithmetic number, because the mean of its divisors is an integer number (10686830333296).

Almost surely, 2^{21373660666591} is an apocalyptic number.

21373660666591 is a deficient number, since it is larger than the sum of its proper divisors (1).

21373660666591 is an equidigital number, since it uses as much as digits as its factorization.

21373660666591 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 44089920, while the sum is 61.

The spelling of 21373660666591 in words is "twenty-one trillion, three hundred seventy-three billion, six hundred sixty million, six hundred sixty-six thousand, five hundred ninety-one".