21021431 has 2 divisors, whose sum is σ = 21021432. Its totient is φ = 21021430.

The previous prime is 21021419. The next prime is 21021449. The reversal of 21021431 is 13412012.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 21021431 - 2¹⁰ = 21020407 is a prime.

It is a super-2 number, since 2×21021431² = 883801122575522, which contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21021331) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10510715 + 10510716.

It is an arithmetic number, because the mean of its divisors is an integer number (10510716).

Almost surely, 2^21021431 is an apocalyptic number.

21021431 is a deficient number, since it is larger than the sum of its proper divisors (1).

21021431 is an equidigital number, since it uses as much as digits as its factorization.

21021431 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 48, while the sum is 14.

The square root of 21021431 is about 4584.9134124867. The cubic root of 21021431 is about 275.9862373240.

Adding to 21021431 its reverse (13412012), we get a palindrome (34433443).

The spelling of 21021431 in words is "twenty-one million, twenty-one thousand, four hundred thirty-one".