21956787591 has 4 divisors (see below), whose sum is σ = 29275716792. Its totient is φ = 14637858392.

The previous prime is 21956787511. The next prime is 21956787617. The reversal of 21956787591 is 19578765912.

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 21956787591 - 2¹³ = 21956779399 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21956787511) 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, 3659464596 + ... + 3659464601.

It is an arithmetic number, because the mean of its divisors is an integer number (7318929198).

Almost surely, 2^21956787591 is an apocalyptic number.

21956787591 is a deficient number, since it is larger than the sum of its proper divisors (7318929201).

21956787591 is an equidigital number, since it uses as much as digits as its factorization.

21956787591 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 7318929200.

The product of its digits is 9525600, while the sum is 60.

The spelling of 21956787591 in words is "twenty-one billion, nine hundred fifty-six million, seven hundred eighty-seven thousand, five hundred ninety-one".