21431057 has 2 divisors, whose sum is σ = 21431058. Its totient is φ = 21431056.

The previous prime is 21431023. The next prime is 21431063. The reversal of 21431057 is 75013412.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 20106256 + 1324801 = 4484^2 + 1151^2 .

It is a cyclic number.

It is not a de Polignac number, because 21431057 - 2¹⁰ = 21430033 is a prime.

It is not a weakly prime, because it can be changed into another prime (21431017) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10715528 + 10715529.

It is an arithmetic number, because the mean of its divisors is an integer number (10715529).

Almost surely, 2^21431057 is an apocalyptic number.

It is an amenable number.

21431057 is a deficient number, since it is larger than the sum of its proper divisors (1).

21431057 is an equidigital number, since it uses as much as digits as its factorization.

21431057 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 840, while the sum is 23.

The square root of 21431057 is about 4629.3689634766. The cubic root of 21431057 is about 277.7673510338.

Adding to 21431057 its reverse (75013412), we get a palindrome (96444469).

The spelling of 21431057 in words is "twenty-one million, four hundred thirty-one thousand, fifty-seven".