21639566287 has 4 divisors (see below), whose sum is σ = 21795246760. Its totient is φ = 21483885816.

The previous prime is 21639566281. The next prime is 21639566293. The reversal of 21639566287 is 78266593612.

It is a semiprime because it is the product of two primes.

It is an interprime number because it is at equal distance from previous prime (21639566281) and next prime (21639566293).

It is a cyclic number.

It is not a de Polignac number, because 21639566287 - 2²⁷ = 21505348559 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21639566281) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 77840028 + ... + 77840305.

It is an arithmetic number, because the mean of its divisors is an integer number (5448811690).

Almost surely, 2^21639566287 is an apocalyptic number.

21639566287 is a deficient number, since it is larger than the sum of its proper divisors (155680473).

21639566287 is a wasteful number, since it uses less digits than its factorization.

21639566287 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 155680472.

The product of its digits is 6531840, while the sum is 55.

The spelling of 21639566287 in words is "twenty-one billion, six hundred thirty-nine million, five hundred sixty-six thousand, two hundred eighty-seven".