90721817 has 4 divisors (see below), whose sum is σ = 93173796. Its totient is φ = 88269840.

The previous prime is 90721801. The next prime is 90721837. The reversal of 90721817 is 71812709.

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

It can be written as a sum of positive squares in 2 ways, for example, as 58049161 + 32672656 = 7619^2 + 5716^2 .

It is a cyclic number.

It is not a de Polignac number, because 90721817 - 2⁴ = 90721801 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (90721837) 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, 1225934 + ... + 1226007.

It is an arithmetic number, because the mean of its divisors is an integer number (23293449).

Almost surely, 2^90721817 is an apocalyptic number.

It is an amenable number.

90721817 is a deficient number, since it is larger than the sum of its proper divisors (2451979).

90721817 is a wasteful number, since it uses less digits than its factorization.

90721817 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2451978.

The product of its (nonzero) digits is 7056, while the sum is 35.

The square root of 90721817 is about 9524.8001028893. The cubic root of 90721817 is about 449.3353430546.

The spelling of 90721817 in words is "ninety million, seven hundred twenty-one thousand, eight hundred seventeen".