18399491 has 16 divisors (see below), whose sum is σ = 21614688. Its totient is φ = 15475200.

The previous prime is 18399487. The next prime is 18399497. The reversal of 18399491 is 19499381.

18399491 = T₇₄₆ + T₇₄₇ + ... + T₈₀₆.

It is a cyclic number.

It is not a de Polignac number, because 18399491 - 2² = 18399487 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (18399497) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 10601 + ... + 12213.

It is an arithmetic number, because the mean of its divisors is an integer number (1350918).

Almost surely, 2^18399491 is an apocalyptic number.

18399491 is a gapful number since it is divisible by the number (11) formed by its first and last digit.

18399491 is a deficient number, since it is larger than the sum of its proper divisors (3215197).

18399491 is a wasteful number, since it uses less digits than its factorization.

18399491 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1702.

The product of its digits is 69984, while the sum is 44.

The square root of 18399491 is about 4289.4627868767. The cubic root of 18399491 is about 263.9987899776.

The spelling of 18399491 in words is "eighteen million, three hundred ninety-nine thousand, four hundred ninety-one".