21666124639 has 2 divisors, whose sum is σ = 21666124640. Its totient is φ = 21666124638.

The previous prime is 21666124621. The next prime is 21666124673. The reversal of 21666124639 is 93642166612.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 21666124639 - 2⁵ = 21666124607 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21666124699) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10833062319 + 10833062320.

It is an arithmetic number, because the mean of its divisors is an integer number (10833062320).

Almost surely, 2^21666124639 is an apocalyptic number.

21666124639 is a deficient number, since it is larger than the sum of its proper divisors (1).

21666124639 is an equidigital number, since it uses as much as digits as its factorization.

21666124639 is an evil number, because the sum of its binary digits is even.

The product of its digits is 559872, while the sum is 46.

The spelling of 21666124639 in words is "twenty-one billion, six hundred sixty-six million, one hundred twenty-four thousand, six hundred thirty-nine".