21657133555 has 4 divisors (see below), whose sum is σ = 25988560272. Its totient is φ = 17325706840.

The previous prime is 21657133517. The next prime is 21657133601. The reversal of 21657133555 is 55533175612.

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

It is not a de Polignac number, because 21657133555 - 2²³ = 21648744947 is a prime.

It is a Duffinian number.

It is an unprimeable number.

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 3 ways as a sum of consecutive naturals, for example, 2165713351 + ... + 2165713360.

It is an arithmetic number, because the mean of its divisors is an integer number (6497140068).

Almost surely, 2^21657133555 is an apocalyptic number.

21657133555 is a deficient number, since it is larger than the sum of its proper divisors (4331426717).

21657133555 is an equidigital number, since it uses as much as digits as its factorization.

21657133555 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 4331426716.

The product of its digits is 472500, while the sum is 43.

The spelling of 21657133555 in words is "twenty-one billion, six hundred fifty-seven million, one hundred thirty-three thousand, five hundred fifty-five".