9090991781 has 4 divisors (see below), whose sum is σ = 9103497312. Its totient is φ = 9078486252.

The previous prime is 9090991751. The next prime is 9090991783. The reversal of 9090991781 is 1871990909.

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.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-9090991781 is a prime.

It is a super-2 number, since 2×9090991781² (a number of 21 digits) contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (9090991783) 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, 6251675 + ... + 6253128.

It is an arithmetic number, because the mean of its divisors is an integer number (2275874328).

Almost surely, 2^9090991781 is an apocalyptic number.

It is an amenable number.

9090991781 is a deficient number, since it is larger than the sum of its proper divisors (12505531).

9090991781 is a wasteful number, since it uses less digits than its factorization.

9090991781 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 12505530.

The product of its (nonzero) digits is 367416, while the sum is 53.

The square root of 9090991781 is about 95346.6925540682. The cubic root of 9090991781 is about 2087.0703503195.

The spelling of 9090991781 in words is "nine billion, ninety million, nine hundred ninety-one thousand, seven hundred eighty-one".