20371991 has 8 divisors (see below), whose sum is σ = 21225600. Its totient is φ = 19530720.

The previous prime is 20371969. The next prime is 20371993. The reversal of 20371991 is 19917302.

It is a happy number.

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 20371991 - 2⁶ = 20371927 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 (20371993) 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, 365 + ... + 6393.

It is an arithmetic number, because the mean of its divisors is an integer number (2653200).

Almost surely, 2^20371991 is an apocalyptic number.

20371991 is a deficient number, since it is larger than the sum of its proper divisors (853609).

20371991 is a wasteful number, since it uses less digits than its factorization.

20371991 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 6169.

The product of its (nonzero) digits is 3402, while the sum is 32.

The square root of 20371991 is about 4513.5342028171. The cubic root of 20371991 is about 273.1143326427.

The spelling of 20371991 in words is "twenty million, three hundred seventy-one thousand, nine hundred ninety-one".