21216523553 has 8 divisors (see below), whose sum is σ = 21312914688. Its totient is φ = 21120178464.

The previous prime is 21216523547. The next prime is 21216523561. The reversal of 21216523553 is 35532561212.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21216523553 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21216523513) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 1195100 + ... + 1212722.

It is an arithmetic number, because the mean of its divisors is an integer number (2664114336).

Almost surely, 2^21216523553 is an apocalyptic number.

It is an amenable number.

21216523553 is a deficient number, since it is larger than the sum of its proper divisors (96391135).

21216523553 is a wasteful number, since it uses less digits than its factorization.

21216523553 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 23023.

The product of its digits is 54000, while the sum is 35.

The spelling of 21216523553 in words is "twenty-one billion, two hundred sixteen million, five hundred twenty-three thousand, five hundred fifty-three".