990991901 has 4 divisors (see below), whose sum is σ = 1000803804. Its totient is φ = 981180000.

The previous prime is 990991871. The next prime is 990991913. The reversal of 990991901 is 109199099.

990991901 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

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 846751801 + 144240100 = 29099^2 + 12010^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-990991901 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (990991301) 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, 4905800 + ... + 4906001.

It is an arithmetic number, because the mean of its divisors is an integer number (250200951).

Almost surely, 2^990991901 is an apocalyptic number.

It is an amenable number.

990991901 is a deficient number, since it is larger than the sum of its proper divisors (9811903).

990991901 is a wasteful number, since it uses less digits than its factorization.

990991901 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 9811902.

The product of its (nonzero) digits is 59049, while the sum is 47.

The square root of 990991901 is about 31480.0238405246. The cubic root of 990991901 is about 996.9882387337.

The spelling of 990991901 in words is "nine hundred ninety million, nine hundred ninety-one thousand, nine hundred one".