20805431 has 2 divisors, whose sum is σ = 20805432. Its totient is φ = 20805430.

The previous prime is 20805427. The next prime is 20805451. The reversal of 20805431 is 13450802.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 20805431 - 2² = 20805427 is a prime.

It is a super-2 number, since 2×20805431² = 865731918191522, which contains 22 as substring.

It is a junction number, because it is equal to n+sod(n) for n = 20805397 and 20805406.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (20805451) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10402715 + 10402716.

It is an arithmetic number, because the mean of its divisors is an integer number (10402716).

Almost surely, 2^20805431 is an apocalyptic number.

20805431 is a deficient number, since it is larger than the sum of its proper divisors (1).

20805431 is an equidigital number, since it uses as much as digits as its factorization.

20805431 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 960, while the sum is 23.

The square root of 20805431 is about 4561.2970742981. The cubic root of 20805431 is about 275.0377072261.

The spelling of 20805431 in words is "twenty million, eight hundred five thousand, four hundred thirty-one".