20405431 has 4 divisors (see below), whose sum is σ = 20414992. Its totient is φ = 20395872.

The previous prime is 20405387. The next prime is 20405443. The reversal of 20405431 is 13450402.

It is a semiprime because it is the product of two primes, and also a brilliant number, because the two primes have the same length.

It is a cyclic number.

It is not a de Polignac number, because 20405431 - 2⁷ = 20405303 is a prime.

It is a super-2 number, since 2×20405431² = 832763228591522, 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 = 20405399 and 20405408.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (20405461) 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, 46 + ... + 6388.

It is an arithmetic number, because the mean of its divisors is an integer number (5103748).

Almost surely, 2^20405431 is an apocalyptic number.

20405431 is a deficient number, since it is larger than the sum of its proper divisors (9561).

20405431 is an equidigital number, since it uses as much as digits as its factorization.

20405431 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 9560.

The product of its (nonzero) digits is 480, while the sum is 19.

The square root of 20405431 is about 4517.2370980501. The cubic root of 20405431 is about 273.2636872261.

Adding to 20405431 its reverse (13450402), we get a palindrome (33855833).

The spelling of 20405431 in words is "twenty million, four hundred five thousand, four hundred thirty-one".