21660787459 has 4 divisors (see below), whose sum is σ = 22069481616. Its totient is φ = 21252093304.

The previous prime is 21660787427. The next prime is 21660787471. The reversal of 21660787459 is 95478706612.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 21660787459 - 2⁵ = 21660787427 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21660787559) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 204346999 + ... + 204347104.

It is an arithmetic number, because the mean of its divisors is an integer number (5517370404).

Almost surely, 2^21660787459 is an apocalyptic number.

21660787459 is a deficient number, since it is larger than the sum of its proper divisors (408694157).

21660787459 is an equidigital number, since it uses as much as digits as its factorization.

21660787459 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 408694156.

The product of its (nonzero) digits is 5080320, while the sum is 55.

The spelling of 21660787459 in words is "twenty-one billion, six hundred sixty million, seven hundred eighty-seven thousand, four hundred fifty-nine".