21533431 has 2 divisors, whose sum is σ = 21533432. Its totient is φ = 21533430.

The previous prime is 21533363. The next prime is 21533443. The reversal of 21533431 is 13433512.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 21533431 - 2⁹ = 21532919 is a prime.

It is a super-2 number, since 2×21533431² = 927377301263522, which contains 22 as substring.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21533471) 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, 10766715 + 10766716.

It is an arithmetic number, because the mean of its divisors is an integer number (10766716).

Almost surely, 2^21533431 is an apocalyptic number.

21533431 is a deficient number, since it is larger than the sum of its proper divisors (1).

21533431 is an equidigital number, since it uses as much as digits as its factorization.

21533431 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 1080, while the sum is 22.

The square root of 21533431 is about 4640.4128049129. The cubic root of 21533431 is about 278.2089375235.

Adding to 21533431 its reverse (13433512), we get a palindrome (34966943).

The spelling of 21533431 in words is "twenty-one million, five hundred thirty-three thousand, four hundred thirty-one".