21020431 has 2 divisors, whose sum is σ = 21020432. Its totient is φ = 21020430.

The previous prime is 21020429. The next prime is 21020437. The reversal of 21020431 is 13402012.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 21020431 - 2¹ = 21020429 is a prime.

It is a super-2 number, since 2×21020431² = 883717038851522, which contains 22 as substring.

Together with 21020429, it forms a pair of twin primes.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21020437) 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, 10510215 + 10510216.

It is an arithmetic number, because the mean of its divisors is an integer number (10510216).

Almost surely, 2^21020431 is an apocalyptic number.

21020431 is a deficient number, since it is larger than the sum of its proper divisors (1).

21020431 is an equidigital number, since it uses as much as digits as its factorization.

21020431 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 48, while the sum is 13.

The square root of 21020431 is about 4584.8043578761. The cubic root of 21020431 is about 275.9818609867.

Adding to 21020431 its reverse (13402012), we get a palindrome (34422443).

The spelling of 21020431 in words is "twenty-one million, twenty thousand, four hundred thirty-one".