21515202231 has 4 divisors (see below), whose sum is σ = 28686936312. Its totient is φ = 14343468152.

The previous prime is 21515202229. The next prime is 21515202251. The reversal of 21515202231 is 13220251512.

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 21515202231 - 2¹ = 21515202229 is a prime.

It is a super-2 number, since 2×21515202231² (a number of 21 digits) contains 22 as substring.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21515202251) 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, 3585867036 + ... + 3585867041.

It is an arithmetic number, because the mean of its divisors is an integer number (7171734078).

Almost surely, 2^21515202231 is an apocalyptic number.

21515202231 is a deficient number, since it is larger than the sum of its proper divisors (7171734081).

21515202231 is an equidigital number, since it uses as much as digits as its factorization.

21515202231 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 7171734080.

The product of its (nonzero) digits is 1200, while the sum is 24.

Adding to 21515202231 its reverse (13220251512), we get a palindrome (34735453743).

The spelling of 21515202231 in words is "twenty-one billion, five hundred fifteen million, two hundred two thousand, two hundred thirty-one".