20197831 has 4 divisors (see below), whose sum is σ = 20667592. Its totient is φ = 19728072.

The previous prime is 20197813. The next prime is 20197843. The reversal of 20197831 is 13879102.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 13879102 = 2 ⋅6939551.

It is a cyclic number.

It is not a de Polignac number, because 20197831 - 2⁵ = 20197799 is a prime.

It is a super-2 number, since 2×20197831² = 815904754209122, 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 = 20197793 and 20197802.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (20197811) 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, 234816 + ... + 234901.

It is an arithmetic number, because the mean of its divisors is an integer number (5166898).

Almost surely, 2^20197831 is an apocalyptic number.

20197831 is a deficient number, since it is larger than the sum of its proper divisors (469761).

20197831 is an equidigital number, since it uses as much as digits as its factorization.

20197831 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 469760.

The product of its (nonzero) digits is 3024, while the sum is 31.

The square root of 20197831 is about 4494.1997062881. The cubic root of 20197831 is about 272.3338200654. Note that the first 3 decimals are identical.

The spelling of 20197831 in words is "twenty million, one hundred ninety-seven thousand, eight hundred thirty-one".