21284475664 has 15 divisors (see below), whose sum is σ = 41239802293. Its totient is φ = 10641946048.

The previous prime is 21284475661. The next prime is 21284475739. The reversal of 21284475664 is 46657448212.

The square root of 21284475664 is 145892.

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., 8241008400 + 13043467264 = 90780^2 + 114208^2 .

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21284475661) by changing a digit.

It is a polite number, since it can be written in 2 ways as a sum of consecutive naturals, for example, 565332 + ... + 601804.

Almost surely, 2^21284475664 is an apocalyptic number.

21284475664 is the 145892-nd square number.

It is an amenable number.

21284475664 is a deficient number, since it is larger than the sum of its proper divisors (19955326629).

21284475664 is an frugal number, since it uses more digits than its factorization.

21284475664 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 72954 (or 36475 counting only the distinct ones).

The product of its digits is 2580480, while the sum is 49.

Multiplying 21284475664 by its sum of digits (49), we get a square (1042939307536 = 1021244²).

The spelling of 21284475664 in words is "twenty-one billion, two hundred eighty-four million, four hundred seventy-five thousand, six hundred sixty-four".