18649991 has 4 divisors (see below), whose sum is σ = 18696000. Its totient is φ = 18603984.

The previous prime is 18649979. The next prime is 18650041. The reversal of 18649991 is 19994681.

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

It is a cyclic number.

It is not a de Polignac number, because 18649991 - 2⁶ = 18649927 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 (18649921) 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, 22391 + ... + 23208.

It is an arithmetic number, because the mean of its divisors is an integer number (4674000).

Almost surely, 2^18649991 is an apocalyptic number.

18649991 is a deficient number, since it is larger than the sum of its proper divisors (46009).

18649991 is an equidigital number, since it uses as much as digits as its factorization.

18649991 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 46008.

The product of its digits is 139968, while the sum is 47.

The square root of 18649991 is about 4318.5635343248. The cubic root of 18649991 is about 265.1914648119.

The spelling of 18649991 in words is "eighteen million, six hundred forty-nine thousand, nine hundred ninety-one".