21645051975 has 36 divisors (see below), whose sum is σ = 38780106456. Its totient is φ = 11540629440.

The previous prime is 21645051941. The next prime is 21645051983. The reversal of 21645051975 is 57915054612.

It is a happy number.

21645051975 is a `hidden beast` number, since 2 + 1 + 6 + 450 + 5 + 197 + 5 = 666.

It is not a de Polignac number, because 21645051975 - 2⁷ = 21645051847 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (45).

It is a self number, because there is not a number n which added to its sum of digits gives 21645051975.

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 35 ways as a sum of consecutive naturals, for example, 875889 + ... + 900261.

Almost surely, 2^21645051975 is an apocalyptic number.

21645051975 is a gapful number since it is divisible by the number (25) formed by its first and last digit.

21645051975 is a deficient number, since it is larger than the sum of its proper divisors (17135054481).

21645051975 is a wasteful number, since it uses less digits than its factorization.

21645051975 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 28336 (or 28328 counting only the distinct ones).

The product of its (nonzero) digits is 378000, while the sum is 45.

The spelling of 21645051975 in words is "twenty-one billion, six hundred forty-five million, fifty-one thousand, nine hundred seventy-five".