21655416640521 has 16 divisors (see below), whose sum is σ = 29488419477504. Its totient is φ = 14129683127184.

The previous prime is 21655416640489. The next prime is 21655416640541. The reversal of 21655416640521 is 12504661455612.

It is a happy number.

It is not a de Polignac number, because 21655416640521 - 2⁵ = 21655416640489 is a prime.

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (21655416640541) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 26185860 + ... + 27000186.

It is an arithmetic number, because the mean of its divisors is an integer number (1843026217344).

Almost surely, 2^{21655416640521} is an apocalyptic number.

It is an amenable number.

21655416640521 is a deficient number, since it is larger than the sum of its proper divisors (7833002836983).

21655416640521 is a wasteful number, since it uses less digits than its factorization.

21655416640521 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1002980.

The product of its (nonzero) digits is 1728000, while the sum is 48.

The spelling of 21655416640521 in words is "twenty-one trillion, six hundred fifty-five billion, four hundred sixteen million, six hundred forty thousand, five hundred twenty-one".