21064643775 has 36 divisors (see below), whose sum is σ = 43118994672. Its totient is φ = 9629550720.

The previous prime is 21064643773. The next prime is 21064643779. The reversal of 21064643775 is 57734646012.

21064643775 is a `hidden beast` number, since 2 + 106 + 46 + 437 + 75 = 666.

It is not a de Polignac number, because 21064643775 - 2¹ = 21064643773 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 21064643775.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21064643773) by changing a digit.

It is a polite number, since it can be written in 35 ways as a sum of consecutive naturals, for example, 6685614 + ... + 6688763.

It is an arithmetic number, because the mean of its divisors is an integer number (1197749852).

Almost surely, 2^21064643775 is an apocalyptic number.

21064643775 is a gapful number since it is divisible by the number (25) formed by its first and last digit.

21064643775 is an abundant number, since it is smaller than the sum of its proper divisors (22054350897).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

21064643775 is a wasteful number, since it uses less digits than its factorization.

21064643775 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 13374400 (or 13374392 counting only the distinct ones).

The product of its (nonzero) digits is 846720, while the sum is 45.

The spelling of 21064643775 in words is "twenty-one billion, sixty-four million, six hundred forty-three thousand, seven hundred seventy-five".