20209831 has 4 divisors (see below), whose sum is σ = 20486752. Its totient is φ = 19932912.

The previous prime is 20209811. The next prime is 20209837. The reversal of 20209831 is 13890202.

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 20209831 - 2¹⁹ = 19685543 is a prime.

It is a super-2 number, since 2×20209831² = 816874538097122, 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 = 20209796 and 20209805.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (20209837) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 138351 + ... + 138496.

It is an arithmetic number, because the mean of its divisors is an integer number (5121688).

Almost surely, 2^20209831 is an apocalyptic number.

20209831 is a deficient number, since it is larger than the sum of its proper divisors (276921).

20209831 is an equidigital number, since it uses as much as digits as its factorization.

20209831 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 276920.

The product of its (nonzero) digits is 864, while the sum is 25.

The square root of 20209831 is about 4495.5345622073. The cubic root of 20209831 is about 272.3877426682.

The spelling of 20209831 in words is "twenty million, two hundred nine thousand, eight hundred thirty-one".