21255593645 has 128 divisors (see below), whose sum is σ = 32930150400. Its totient is φ = 12933043200.

The previous prime is 21255593617. The next prime is 21255593669. The reversal of 21255593645 is 54639555212.

It is not a de Polignac number, because 21255593645 - 2⁶ = 21255593581 is a prime.

It is a super-3 number, since 3×21255593645³ (a number of 32 digits) contains 333 as substring. Note that it is a super-d number also for d = 2.

It is a Curzon number.

It is a self number, because there is not a number n which added to its sum of digits gives 21255593645.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 127 ways as a sum of consecutive naturals, for example, 64216130 + ... + 64216460.

It is an arithmetic number, because the mean of its divisors is an integer number (257266800).

Almost surely, 2^21255593645 is an apocalyptic number.

It is an amenable number.

21255593645 is a deficient number, since it is larger than the sum of its proper divisors (11674556755).

21255593645 is a wasteful number, since it uses less digits than its factorization.

21255593645 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 571.

The product of its digits is 1620000, while the sum is 47.

The spelling of 21255593645 in words is "twenty-one billion, two hundred fifty-five million, five hundred ninety-three thousand, six hundred forty-five".