21558635639 has 2 divisors, whose sum is σ = 21558635640. Its totient is φ = 21558635638.

The previous prime is 21558635611. The next prime is 21558635647. The reversal of 21558635639 is 93653685512.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 21558635639 - 2³² = 17263668343 is a prime.

It is a Sophie Germain prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21558635669) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10779317819 + 10779317820.

It is an arithmetic number, because the mean of its divisors is an integer number (10779317820).

Almost surely, 2^21558635639 is an apocalyptic number.

21558635639 is a deficient number, since it is larger than the sum of its proper divisors (1).

21558635639 is an equidigital number, since it uses as much as digits as its factorization.

21558635639 is an evil number, because the sum of its binary digits is even.

The product of its digits is 5832000, while the sum is 53.

The spelling of 21558635639 in words is "twenty-one billion, five hundred fifty-eight million, six hundred thirty-five thousand, six hundred thirty-nine".