18972257 has 4 divisors (see below), whose sum is σ = 18981936. Its totient is φ = 18962580.

The previous prime is 18972229. The next prime is 18972269. The reversal of 18972257 is 75227981.

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, and also a brilliant number, because the two primes have the same length.

It is a cyclic number.

It is not a de Polignac number, because 18972257 - 2⁶ = 18972193 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (18972287) 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, 743 + ... + 6204.

It is an arithmetic number, because the mean of its divisors is an integer number (4745484).

Almost surely, 2^18972257 is an apocalyptic number.

It is an amenable number.

18972257 is a deficient number, since it is larger than the sum of its proper divisors (9679).

18972257 is an equidigital number, since it uses as much as digits as its factorization.

18972257 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 9678.

The product of its digits is 70560, while the sum is 41.

The square root of 18972257 is about 4355.7154406595. The cubic root of 18972257 is about 266.7102253498.

The spelling of 18972257 in words is "eighteen million, nine hundred seventy-two thousand, two hundred fifty-seven".