90091993 has 6 divisors (see below), whose sum is σ = 95703566. Its totient is φ = 84792192.

The previous prime is 90091979. The next prime is 90092017. The reversal of 90091993 is 39919009.

It can be written as a sum of positive squares in 3 ways, for example, as 62916624 + 27175369 = 7932^2 + 5213^2 .

It is a de Polignac number, because none of the positive numbers 2^k-90091993 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (90091973) by changing a digit.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 155580 + ... + 156157.

Almost surely, 2^90091993 is an apocalyptic number.

It is an amenable number.

90091993 is a deficient number, since it is larger than the sum of its proper divisors (5611573).

90091993 is a wasteful number, since it uses less digits than its factorization.

90091993 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 311771 (or 311754 counting only the distinct ones).

The product of its (nonzero) digits is 19683, while the sum is 40.

The square root of 90091993 is about 9491.6801989953. The cubic root of 90091993 is about 448.2931107610.

The spelling of 90091993 in words is "ninety million, ninety-one thousand, nine hundred ninety-three".