18722591 has 4 divisors (see below), whose sum is σ = 19120992. Its totient is φ = 18324192.

The previous prime is 18722573. The next prime is 18722597. The reversal of 18722591 is 19522781.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-18722591 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 (18722597) 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, 199130 + ... + 199223.

It is an arithmetic number, because the mean of its divisors is an integer number (4780248).

Almost surely, 2^18722591 is an apocalyptic number.

18722591 is a deficient number, since it is larger than the sum of its proper divisors (398401).

18722591 is an equidigital number, since it uses as much as digits as its factorization.

18722591 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 398400.

The product of its digits is 10080, while the sum is 35.

The square root of 18722591 is about 4326.9609427403. The cubic root of 18722591 is about 265.5351284614.

The spelling of 18722591 in words is "eighteen million, seven hundred twenty-two thousand, five hundred ninety-one".