21688561006501 has 4 divisors (see below), whose sum is σ = 21688724605600. Its totient is φ = 21688397407404.

The previous prime is 21688561006477. The next prime is 21688561006507. The reversal of 21688561006501 is 10560016588612.

It is a happy number.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 21688561006501 - 2³⁷ = 21551122053029 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 (21688561006507) 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, 81600531 + ... + 81865888.

It is an arithmetic number, because the mean of its divisors is an integer number (5422181151400).

Almost surely, 2^{21688561006501} is an apocalyptic number.

It is an amenable number.

21688561006501 is a deficient number, since it is larger than the sum of its proper divisors (163599099).

21688561006501 is a wasteful number, since it uses less digits than its factorization.

21688561006501 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 163599098.

The product of its (nonzero) digits is 691200, while the sum is 49.

The spelling of 21688561006501 in words is "twenty-one trillion, six hundred eighty-eight billion, five hundred sixty-one million, six thousand, five hundred one".