21987184251 has 8 divisors (see below), whose sum is σ = 30108576784. Its totient is φ = 14261957280.

The previous prime is 21987184211. The next prime is 21987184253. The reversal of 21987184251 is 15248178912.

It is a happy number.

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

It is not a de Polignac number, because 21987184251 - 2⁶ = 21987184187 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 21987184251.

It is not an unprimeable number, because it can be changed into a prime (21987184253) 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, 99041260 + ... + 99041481.

It is an arithmetic number, because the mean of its divisors is an integer number (3763572098).

Almost surely, 2^21987184251 is an apocalyptic number.

21987184251 is a deficient number, since it is larger than the sum of its proper divisors (8121392533).

21987184251 is a wasteful number, since it uses less digits than its factorization.

21987184251 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 198082781.

The product of its digits is 322560, while the sum is 48.

The spelling of 21987184251 in words is "twenty-one billion, nine hundred eighty-seven million, one hundred eighty-four thousand, two hundred fifty-one".