90018721 has 16 divisors (see below), whose sum is σ = 99107008. Its totient is φ = 81259200.

The previous prime is 90018703. The next prime is 90018767. The reversal of 90018721 is 12781009.

It is a cyclic number.

It is not a de Polignac number, because 90018721 - 2¹⁵ = 89985953 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 90018721.

It is not an unprimeable number, because it can be changed into a prime (90018781) 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, 157366 + ... + 157936.

It is an arithmetic number, because the mean of its divisors is an integer number (6194188).

Almost surely, 2^90018721 is an apocalyptic number.

It is an amenable number.

90018721 is a deficient number, since it is larger than the sum of its proper divisors (9088287).

90018721 is a wasteful number, since it uses less digits than its factorization.

90018721 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 832.

The product of its (nonzero) digits is 1008, while the sum is 28.

The square root of 90018721 is about 9487.8196125348. The cubic root of 90018721 is about 448.1715452342.

The spelling of 90018721 in words is "ninety million, eighteen thousand, seven hundred twenty-one".