21751486391 has 4 divisors (see below), whose sum is σ = 22049452032. Its totient is φ = 21453520752.

The previous prime is 21751486369. The next prime is 21751486397. The reversal of 21751486391 is 19368415712.

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 21751486391 - 2⁶ = 21751486327 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21751486397) 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, 148982711 + ... + 148982856.

It is an arithmetic number, because the mean of its divisors is an integer number (5512363008).

Almost surely, 2^21751486391 is an apocalyptic number.

21751486391 is a deficient number, since it is larger than the sum of its proper divisors (297965641).

21751486391 is an equidigital number, since it uses as much as digits as its factorization.

21751486391 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 297965640.

The product of its digits is 362880, while the sum is 47.

The spelling of 21751486391 in words is "twenty-one billion, seven hundred fifty-one million, four hundred eighty-six thousand, three hundred ninety-one".