21402531406369 has 9 divisors (see below), whose sum is σ = 21601195259763. Its totient is φ = 21205678268232.

The previous prime is 21402531406367. The next prime is 21402531406387. The reversal of 21402531406369 is 96360413520412.

The square root of 21402531406369 is 4626287.

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., 14917461709969 + 6485069696400 = 3862313^2 + 2546580^2 .

It is not a de Polignac number, because 21402531406369 - 2¹ = 21402531406367 is a prime.

It is a super-2 number, since 2×21402531406369² (a number of 27 digits) contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21402531406367) 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, 504244062 + ... + 504286504.

Almost surely, 2^{21402531406369} is an apocalyptic number.

21402531406369 is the 4626287-th square number.

21402531406369 is the 2313144-th centered octagonal number.

It is an amenable number.

21402531406369 is a deficient number, since it is larger than the sum of its proper divisors (198663853394).

21402531406369 is an frugal number, since it uses more digits than its factorization.

21402531406369 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 85104 (or 42552 counting only the distinct ones).

The product of its (nonzero) digits is 933120, while the sum is 46.

It can be divided in two parts, 21402531 and 406369, that added together give a square (21808900 = 4670²).

The spelling of 21402531406369 in words is "twenty-one trillion, four hundred two billion, five hundred thirty-one million, four hundred six thousand, three hundred sixty-nine".