991209901 has 8 divisors (see below), whose sum is σ = 1087572384. Its totient is φ = 895889520.

The previous prime is 991209893. The next prime is 991209911. The reversal of 991209901 is 109902199.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 991209901 - 2³ = 991209893 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 (991209911) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 258531 + ... + 262336.

It is an arithmetic number, because the mean of its divisors is an integer number (135946548).

Almost surely, 2^991209901 is an apocalyptic number.

It is an amenable number.

991209901 is a deficient number, since it is larger than the sum of its proper divisors (96362483).

991209901 is a wasteful number, since it uses less digits than its factorization.

991209901 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 521051.

The product of its (nonzero) digits is 13122, while the sum is 40.

The square root of 991209901 is about 31483.4861633841. The cubic root of 991209901 is about 997.0613397350.

It can be divided in two parts, 99 and 1209901, that added together give a square (1210000 = 1100²).

The spelling of 991209901 in words is "nine hundred ninety-one million, two hundred nine thousand, nine hundred one".