21688747441 has 9 divisors (see below), whose sum is σ = 23042263531. Its totient is φ = 20410582432.

The previous prime is 21688747429. The next prime is 21688747459. The reversal of 21688747441 is 14474788612.

The square root of 21688747441 is 147271.

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., 16885703025 + 4803044416 = 129945^2 + 69304^2 .

It is not a de Polignac number, because 21688747441 - 2²⁵ = 21655193009 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21688747541) 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, 2499276 + ... + 2507938.

Almost surely, 2^21688747441 is an apocalyptic number.

21688747441 is the 147271-st square number.

21688747441 is the 73636-th centered octagonal number.

It is an amenable number.

21688747441 is a deficient number, since it is larger than the sum of its proper divisors (1353516090).

21688747441 is an frugal number, since it uses more digits than its factorization.

21688747441 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 17360 (or 8680 counting only the distinct ones).

The product of its digits is 2408448, while the sum is 52.

It can be divided in two parts, 21688 and 747441, that added together give a square (769129 = 877²).

The spelling of 21688747441 in words is "twenty-one billion, six hundred eighty-eight million, seven hundred forty-seven thousand, four hundred forty-one".