21315313655 has 8 divisors (see below), whose sum is σ = 25579382784. Its totient is φ = 17051580000.

The previous prime is 21315313633. The next prime is 21315313661. The reversal of 21315313655 is 55631351312.

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

It is not a de Polignac number, because 21315313655 - 2¹⁰ = 21315312631 is a prime.

It is a super-2 number, since 2×21315313655² (a number of 21 digits) contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

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, 87905 + ... + 224405.

It is an arithmetic number, because the mean of its divisors is an integer number (3197422848).

Almost surely, 2^21315313655 is an apocalyptic number.

21315313655 is a deficient number, since it is larger than the sum of its proper divisors (4264069129).

21315313655 is a wasteful number, since it uses less digits than its factorization.

21315313655 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 167737.

The product of its digits is 40500, while the sum is 35.

Adding to 21315313655 its reverse (55631351312), we get a palindrome (76946664967).

The spelling of 21315313655 in words is "twenty-one billion, three hundred fifteen million, three hundred thirteen thousand, six hundred fifty-five".