21516536531 has 8 divisors (see below), whose sum is σ = 24591592704. Its totient is φ = 18441796680.

The previous prime is 21516536449. The next prime is 21516536549. The reversal of 21516536531 is 13563561512.

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-21516536531 is a prime.

It is a super-2 number, since 2×21516536531² (a number of 21 digits) contains 22 as substring.

It is not an unprimeable number, because it can be changed into a prime (21516535531) 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, 91106 + ... + 226568.

It is an arithmetic number, because the mean of its divisors is an integer number (3073949088).

Almost surely, 2^21516536531 is an apocalyptic number.

21516536531 is a deficient number, since it is larger than the sum of its proper divisors (3075056173).

21516536531 is a wasteful number, since it uses less digits than its factorization.

21516536531 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 158161.

The product of its digits is 81000, while the sum is 38.

The spelling of 21516536531 in words is "twenty-one billion, five hundred sixteen million, five hundred thirty-six thousand, five hundred thirty-one".