18413721 has 18 divisors (see below), whose sum is σ = 27496170. Its totient is φ = 11874240.

The previous prime is 18413719. The next prime is 18413741. The reversal of 18413721 is 12731481.

It can be written as a sum of positive squares in only one way, i.e., 13838400 + 4575321 = 3720^2 + 2139^2 .

It is not a de Polignac number, because 18413721 - 2¹ = 18413719 is a prime.

It is not an unprimeable number, because it can be changed into a prime (18413741) by changing a digit.

It is a polite number, since it can be written in 17 ways as a sum of consecutive naturals, for example, 7585 + ... + 9713.

It is an arithmetic number, because the mean of its divisors is an integer number (1527565).

Almost surely, 2^18413721 is an apocalyptic number.

It is an amenable number.

18413721 is a deficient number, since it is larger than the sum of its proper divisors (9082449).

18413721 is a wasteful number, since it uses less digits than its factorization.

18413721 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2197 (or 2163 counting only the distinct ones).

The product of its digits is 1344, while the sum is 27.

The square root of 18413721 is about 4291.1211821621. The cubic root of 18413721 is about 264.0668305325.

The spelling of 18413721 in words is "eighteen million, four hundred thirteen thousand, seven hundred twenty-one".