21660135506 has 64 divisors (see below), whose sum is σ = 36827260416. Its totient is φ = 9499776000.

The previous prime is 21660135503. The next prime is 21660135551. The reversal of 21660135506 is 60553106612.

It is a super-2 number, since 2×21660135506² (a number of 21 digits) contains 22 as substring.

It is not an unprimeable number, because it can be changed into a prime (21660135503) by changing a digit.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 6256616 + ... + 6260076.

It is an arithmetic number, because the mean of its divisors is an integer number (575425944).

Almost surely, 2^21660135506 is an apocalyptic number.

21660135506 is a deficient number, since it is larger than the sum of its proper divisors (15167124910).

21660135506 is a wasteful number, since it uses less digits than its factorization.

21660135506 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3707.

The product of its (nonzero) digits is 32400, while the sum is 35.

The spelling of 21660135506 in words is "twenty-one billion, six hundred sixty million, one hundred thirty-five thousand, five hundred six".