21315991651 has 8 divisors (see below), whose sum is σ = 21410796960. Its totient is φ = 21221395392.

The previous prime is 21315991633. The next prime is 21315991661. The reversal of 21315991651 is 15619951312.

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 21315991651 - 2¹¹ = 21315989603 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 21315991598 and 21315991607.

It is not an unprimeable number, because it can be changed into a prime (21315991621) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 153921 + ... + 257533.

It is an arithmetic number, because the mean of its divisors is an integer number (2676349620).

Almost surely, 2^21315991651 is an apocalyptic number.

21315991651 is a deficient number, since it is larger than the sum of its proper divisors (94805309).

21315991651 is a wasteful number, since it uses less digits than its factorization.

21315991651 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 104525.

The product of its digits is 72900, while the sum is 43.

The spelling of 21315991651 in words is "twenty-one billion, three hundred fifteen million, nine hundred ninety-one thousand, six hundred fifty-one".