18978157 has 4 divisors (see below), whose sum is σ = 20703456. Its totient is φ = 17252860.

The previous prime is 18978119. The next prime is 18978161. The reversal of 18978157 is 75187981.

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 a de Polignac number, because none of the positive numbers 2^k-18978157 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 (18978257) 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, 862633 + ... + 862654.

It is an arithmetic number, because the mean of its divisors is an integer number (5175864).

Almost surely, 2^18978157 is an apocalyptic number.

It is an amenable number.

18978157 is a deficient number, since it is larger than the sum of its proper divisors (1725299).

18978157 is a wasteful number, since it uses less digits than its factorization.

18978157 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1725298.

The product of its digits is 141120, while the sum is 46.

The square root of 18978157 is about 4356.3926590701. The cubic root of 18978157 is about 266.7378697016.

The spelling of 18978157 in words is "eighteen million, nine hundred seventy-eight thousand, one hundred fifty-seven".