21917423581 has 4 divisors (see below), whose sum is σ = 21918679072. Its totient is φ = 21916168092.

The previous prime is 21917423573. The next prime is 21917423599. The reversal of 21917423581 is 18532471912.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 21917423581 - 2³ = 21917423573 is a prime.

It is a super-2 number, since 2×21917423581² (a number of 21 digits) contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21917423501) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 601185 + ... + 636598.

It is an arithmetic number, because the mean of its divisors is an integer number (5479669768).

Almost surely, 2^21917423581 is an apocalyptic number.

It is an amenable number.

21917423581 is a deficient number, since it is larger than the sum of its proper divisors (1255491).

21917423581 is a wasteful number, since it uses less digits than its factorization.

21917423581 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1255490.

The product of its digits is 120960, while the sum is 43.

The spelling of 21917423581 in words is "twenty-one billion, nine hundred seventeen million, four hundred twenty-three thousand, five hundred eighty-one".