21345431 has 2 divisors, whose sum is σ = 21345432. Its totient is φ = 21345430.

The previous prime is 21345427. The next prime is 21345451. The reversal of 21345431 is 13454312.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 21345431 - 2² = 21345427 is a prime.

It is a super-2 number, since 2×21345431² = 911254849151522, which contains 22 as substring.

It is a Sophie Germain prime.

It is a Chen prime.

It is a junction number, because it is equal to n+sod(n) for n = 21345397 and 21345406.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21345451) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10672715 + 10672716.

It is an arithmetic number, because the mean of its divisors is an integer number (10672716).

Almost surely, 2^21345431 is an apocalyptic number.

21345431 is a deficient number, since it is larger than the sum of its proper divisors (1).

21345431 is an equidigital number, since it uses as much as digits as its factorization.

21345431 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 1440, while the sum is 23.

The square root of 21345431 is about 4620.1115787392. Note that the first 3 decimals coincide. The cubic root of 21345431 is about 277.3969251685.

Adding to 21345431 its reverse (13454312), we get a palindrome (34799743).

The spelling of 21345431 in words is "twenty-one million, three hundred forty-five thousand, four hundred thirty-one".