21608118009 has 15 divisors (see below), whose sum is σ = 32280769983. Its totient is φ = 14404530024.

The previous prime is 21608117957. The next prime is 21608118043. The reversal of 21608118009 is 90081180612.

The square root of 21608118009 is 146997.

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., 1622075625 + 19986042384 = 40275^2 + 141372^2 .

It is not a de Polignac number, because 21608118009 - 2¹¹ = 21608115961 is a prime.

It is not an unprimeable number, because it can be changed into a prime (21608118409) by changing a digit.

It is a polite number, since it can be written in 14 ways as a sum of consecutive naturals, for example, 1314807 + ... + 1331139.

Almost surely, 2^21608118009 is an apocalyptic number.

21608118009 is the 146997-th square number.

21608118009 is the 73499-th centered octagonal number.

It is an amenable number.

21608118009 is a deficient number, since it is larger than the sum of its proper divisors (10672651974).

21608118009 is an frugal number, since it uses more digits than its factorization.

21608118009 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 32678 (or 16336 counting only the distinct ones).

The product of its (nonzero) digits is 6912, while the sum is 36.

Multiplying 21608118009 by its sum of digits (36), we get a square (777892248324 = 881982²).

The spelling of 21608118009 in words is "twenty-one billion, six hundred eight million, one hundred eighteen thousand, nine".