20491931 has 4 divisors (see below), whose sum is σ = 20504232. Its totient is φ = 20479632.

The previous prime is 20491909. The next prime is 20491957. The reversal of 20491931 is 13919402.

It is a happy number.

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

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-20491931 is a prime.

It is a super-2 number, since 2×20491931² = 839838472217522, which contains 22 as substring.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 20491894 and 20491903.

It is not an unprimeable number, because it can be changed into a prime (20491901) 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, 3170 + ... + 7143.

It is an arithmetic number, because the mean of its divisors is an integer number (5126058).

Almost surely, 2^20491931 is an apocalyptic number.

20491931 is a deficient number, since it is larger than the sum of its proper divisors (12301).

20491931 is a wasteful number, since it uses less digits than its factorization.

20491931 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 12300.

The product of its (nonzero) digits is 1944, while the sum is 29.

The square root of 20491931 is about 4526.8014093839. The cubic root of 20491931 is about 273.6492706415.

The spelling of 20491931 in words is "twenty million, four hundred ninety-one thousand, nine hundred thirty-one".