21628771645 has 16 divisors (see below), whose sum is σ = 29595207600. Its totient is φ = 15032484864.

The previous prime is 21628771631. The next prime is 21628771649. The reversal of 21628771645 is 54617782612.

It can be written as a sum of positive squares in 8 ways, for example, as 4550986521 + 17077785124 = 67461^2 + 130682^2 .

It is a cyclic number.

It is not a de Polignac number, because 21628771645 - 2⁵ = 21628771613 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21628771649) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 9785670 + ... + 9787879.

It is an arithmetic number, because the mean of its divisors is an integer number (1849700475).

Almost surely, 2^21628771645 is an apocalyptic number.

It is an amenable number.

21628771645 is a deficient number, since it is larger than the sum of its proper divisors (7966435955).

21628771645 is a wasteful number, since it uses less digits than its factorization.

21628771645 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 19573584.

The product of its digits is 1128960, while the sum is 49.

The spelling of 21628771645 in words is "twenty-one billion, six hundred twenty-eight million, seven hundred seventy-one thousand, six hundred forty-five".