90978809 has 4 divisors (see below), whose sum is σ = 90998004. Its totient is φ = 90959616.

The previous prime is 90978787. The next prime is 90978827. The reversal of 90978809 is 90887909.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 90887909 = 7 ⋅12983987.

It can be written as a sum of positive squares in 2 ways, for example, as 40284409 + 50694400 = 6347^2 + 7120^2 .

It is a cyclic number.

It is not a de Polignac number, because 90978809 - 2⁸ = 90978553 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (90978109) 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, 3209 + ... + 13865.

It is an arithmetic number, because the mean of its divisors is an integer number (22749501).

Almost surely, 2^90978809 is an apocalyptic number.

It is an amenable number.

90978809 is a deficient number, since it is larger than the sum of its proper divisors (19195).

90978809 is a wasteful number, since it uses less digits than its factorization.

90978809 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 19194.

The product of its (nonzero) digits is 326592, while the sum is 50.

The square root of 90978809 is about 9538.2812393009. The cubic root of 90978809 is about 449.7592275763.

The spelling of 90978809 in words is "ninety million, nine hundred seventy-eight thousand, eight hundred nine".