21511652251 has 4 divisors (see below), whose sum is σ = 21524330232. Its totient is φ = 21498974272.

The previous prime is 21511652231. The next prime is 21511652293. The reversal of 21511652251 is 15225611512.

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 21511652251 - 2⁹ = 21511651739 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21511652231) 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, 6336445 + ... + 6339838.

It is an arithmetic number, because the mean of its divisors is an integer number (5381082558).

Almost surely, 2^21511652251 is an apocalyptic number.

21511652251 is a deficient number, since it is larger than the sum of its proper divisors (12677981).

21511652251 is a wasteful number, since it uses less digits than its factorization.

21511652251 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 12677980.

The product of its digits is 6000, while the sum is 31.

The spelling of 21511652251 in words is "twenty-one billion, five hundred eleven million, six hundred fifty-two thousand, two hundred fifty-one".