18391690 has 8 divisors (see below), whose sum is σ = 33105060. Its totient is φ = 7356672.

The previous prime is 18391673. The next prime is 18391699. The reversal of 18391690 is 9619381.

It can be written as a sum of positive squares in 2 ways, for example, as 15705369 + 2686321 = 3963^2 + 1639^2 .

It is a sphenic number, since it is the product of 3 distinct primes.

It is a super-2 number, since 2×18391690² = 676508522112200, which contains 22 as substring.

It is not an unprimeable number, because it can be changed into a prime (18391699) 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, 919575 + ... + 919594.

Almost surely, 2^18391690 is an apocalyptic number.

18391690 is a gapful number since it is divisible by the number (10) formed by its first and last digit.

18391690 is a deficient number, since it is larger than the sum of its proper divisors (14713370).

18391690 is a wasteful number, since it uses less digits than its factorization.

18391690 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1839176.

The product of its (nonzero) digits is 11664, while the sum is 37.

The square root of 18391690 is about 4288.5533691444. The cubic root of 18391690 is about 263.9614747120.

The spelling of 18391690 in words is "eighteen million, three hundred ninety-one thousand, six hundred ninety".