21315641665 has 8 divisors (see below), whose sum is σ = 25617588480. Its totient is φ = 17026634352.

The previous prime is 21315641639. The next prime is 21315641681. The reversal of 21315641665 is 56614651312.

It is a happy number.

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

It is a cyclic number.

It is not a de Polignac number, because 21315641665 - 2⁷ = 21315641537 is a prime.

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 3231249 + ... + 3237838.

It is an arithmetic number, because the mean of its divisors is an integer number (3202198560).

Almost surely, 2^21315641665 is an apocalyptic number.

It is an amenable number.

21315641665 is a deficient number, since it is larger than the sum of its proper divisors (4301946815).

21315641665 is an equidigital number, since it uses as much as digits as its factorization.

21315641665 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 6469751.

The product of its digits is 129600, while the sum is 40.

The spelling of 21315641665 in words is "twenty-one billion, three hundred fifteen million, six hundred forty-one thousand, six hundred sixty-five".