21764215729 has 9 divisors (see below), whose sum is σ = 21931752171. Its totient is φ = 21597952800.

The previous prime is 21764215723. The next prime is 21764215751. The reversal of 21764215729 is 92751246712.

The square root of 21764215729 is 147527.

It is a perfect power (a square), and thus also a powerful number.

It can be written as a sum of positive squares in only one way, i.e., 20361863025 + 1402352704 = 142695^2 + 37448^2 .

It is not a de Polignac number, because 21764215729 - 2¹³ = 21764207537 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21764215723) by changing a digit.

It is a polite number, since it can be written in 8 ways as a sum of consecutive naturals, for example, 22276089 + ... + 22277065.

Almost surely, 2^21764215729 is an apocalyptic number.

21764215729 is the 147527-th square number.

21764215729 is the 73764-th centered octagonal number.

It is an amenable number.

21764215729 is a deficient number, since it is larger than the sum of its proper divisors (167536442).

21764215729 is an frugal number, since it uses more digits than its factorization.

21764215729 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2256 (or 1128 counting only the distinct ones).

The product of its digits is 423360, while the sum is 46.

The spelling of 21764215729 in words is "twenty-one billion, seven hundred sixty-four million, two hundred fifteen thousand, seven hundred twenty-nine".