90781 has 4 divisors (see below), whose sum is σ = 94752. Its totient is φ = 86812.

The previous prime is 90749. The next prime is 90787. The reversal of 90781 is 18709.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4, and also an emirpimes, since its reverse is a distinct semiprime: 18709 = 53 ⋅353.

It is a cyclic number.

It is not a de Polignac number, because 90781 - 2⁵ = 90749 is a prime.

It is a super-2 number, since 2×90781² = 16482379922, which contains 22 as substring.

It is an alternating number because its digits alternate between odd and even.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (90787) 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, 1951 + ... + 1996.

It is an arithmetic number, because the mean of its divisors is an integer number (23688).

2⁹⁰⁷⁸¹ is an apocalyptic number.

It is an amenable number.

90781 is a deficient number, since it is larger than the sum of its proper divisors (3971).

90781 is a wasteful number, since it uses less digits than its factorization.

90781 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3970.

The product of its (nonzero) digits is 504, while the sum is 25.

The square root of 90781 is about 301.2988549597. The cubic root of 90781 is about 44.9433030814.

The spelling of 90781 in words is "ninety thousand, seven hundred eighty-one".