21298553665 has 16 divisors (see below), whose sum is σ = 26887723200. Its totient is φ = 16172454592.

The previous prime is 21298553663. The next prime is 21298553693. The reversal of 21298553665 is 56635589212.

It is a happy number.

It is not a de Polignac number, because 21298553665 - 2¹ = 21298553663 is a prime.

It is not an unprimeable number, because it can be changed into a prime (21298553663) 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, 1236247 + ... + 1253356.

It is an arithmetic number, because the mean of its divisors is an integer number (1680482700).

Almost surely, 2^21298553665 is an apocalyptic number.

It is an amenable number.

21298553665 is a deficient number, since it is larger than the sum of its proper divisors (5589169535).

21298553665 is a wasteful number, since it uses less digits than its factorization.

21298553665 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2489696.

The product of its digits is 3888000, while the sum is 52.

The spelling of 21298553665 in words is "twenty-one billion, two hundred ninety-eight million, five hundred fifty-three thousand, six hundred sixty-five".