21993782591 has 16 divisors (see below), whose sum is σ = 25174775808. Its totient is φ = 19019325600.

The previous prime is 21993782581. The next prime is 21993782597. The reversal of 21993782591 is 19528739912.

It is a de Polignac number, because none of the positive numbers 2^k-21993782591 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 (21993782597) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 194351 + ... + 285936.

It is an arithmetic number, because the mean of its divisors is an integer number (1573423488).

Almost surely, 2^21993782591 is an apocalyptic number.

21993782591 is a deficient number, since it is larger than the sum of its proper divisors (3180993217).

21993782591 is a wasteful number, since it uses less digits than its factorization.

21993782591 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 480502.

The product of its digits is 2449440, while the sum is 56.

The spelling of 21993782591 in words is "twenty-one billion, nine hundred ninety-three million, seven hundred eighty-two thousand, five hundred ninety-one".