901991 has 4 divisors (see below), whose sum is σ = 941232. Its totient is φ = 862752.

The previous prime is 901973. The next prime is 901993. The reversal of 901991 is 199109.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 901991 - 2¹⁴ = 885607 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 (901993) 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, 19586 + ... + 19631.

It is an arithmetic number, because the mean of its divisors is an integer number (235308).

2⁹⁰¹⁹⁹¹ is an apocalyptic number.

901991 is a deficient number, since it is larger than the sum of its proper divisors (39241).

901991 is a wasteful number, since it uses less digits than its factorization.

901991 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 39240.

The product of its (nonzero) digits is 729, while the sum is 29.

The square root of 901991 is about 949.7320674801. The cubic root of 901991 is about 96.6200819270.

The spelling of 901991 in words is "nine hundred one thousand, nine hundred ninety-one".