90190721 has 4 divisors (see below), whose sum is σ = 90226500. Its totient is φ = 90154944.

The previous prime is 90190717. The next prime is 90190733. The reversal of 90190721 is 12709109.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 12709109 = 7 ⋅1815587.

It can be written as a sum of positive squares in 2 ways, for example, as 38925121 + 51265600 = 6239^2 + 7160^2 .

It is a cyclic number.

It is not a de Polignac number, because 90190721 - 2² = 90190717 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (90190741) 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, 13796 + ... + 19253.

It is an arithmetic number, because the mean of its divisors is an integer number (22556625).

Almost surely, 2^90190721 is an apocalyptic number.

It is an amenable number.

90190721 is a deficient number, since it is larger than the sum of its proper divisors (35779).

90190721 is a wasteful number, since it uses less digits than its factorization.

90190721 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 35778.

The product of its (nonzero) digits is 1134, while the sum is 29.

The square root of 90190721 is about 9496.8795401437. The cubic root of 90190721 is about 448.4568061253.

The spelling of 90190721 in words is "ninety million, one hundred ninety thousand, seven hundred twenty-one".