21430531 has 2 divisors, whose sum is σ = 21430532. Its totient is φ = 21430530.

The previous prime is 21430529. The next prime is 21430559. The reversal of 21430531 is 13503412.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 21430531 - 2¹ = 21430529 is a prime.

It is a super-2 number, since 2×21430531² = 918535317883922, which contains 22 as substring.

Together with 21430529, it forms a pair of twin primes.

It is a junction number, because it is equal to n+sod(n) for n = 21430499 and 21430508.

It is not a weakly prime, because it can be changed into another prime (21430561) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10715265 + 10715266.

It is an arithmetic number, because the mean of its divisors is an integer number (10715266).

Almost surely, 2^21430531 is an apocalyptic number.

21430531 is a deficient number, since it is larger than the sum of its proper divisors (1).

21430531 is an equidigital number, since it uses as much as digits as its factorization.

21430531 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 360, while the sum is 19.

The square root of 21430531 is about 4629.3121519293. The cubic root of 21430531 is about 277.7650785246.

Adding to 21430531 its reverse (13503412), we get a palindrome (34933943).

The spelling of 21430531 in words is "twenty-one million, four hundred thirty thousand, five hundred thirty-one".