21136640491 has 2 divisors, whose sum is σ = 21136640492. Its totient is φ = 21136640490.

The previous prime is 21136640479. The next prime is 21136640507. The reversal of 21136640491 is 19404663112.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 21136640491 - 2⁷ = 21136640363 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 21136640491.

It is not a weakly prime, because it can be changed into another prime (21136640471) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10568320245 + 10568320246.

It is an arithmetic number, because the mean of its divisors is an integer number (10568320246).

Almost surely, 2^21136640491 is an apocalyptic number.

21136640491 is a deficient number, since it is larger than the sum of its proper divisors (1).

21136640491 is an equidigital number, since it uses as much as digits as its factorization.

21136640491 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 31104, while the sum is 37.

The spelling of 21136640491 in words is "twenty-one billion, one hundred thirty-six million, six hundred forty thousand, four hundred ninety-one".