21432991 has 2 divisors, whose sum is σ = 21432992. Its totient is φ = 21432990.

The previous prime is 21432979. The next prime is 21433051. The reversal of 21432991 is 19923412.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 21432991 - 2²¹ = 19335839 is a prime.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21432091) 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, 10716495 + 10716496.

It is an arithmetic number, because the mean of its divisors is an integer number (10716496).

Almost surely, 2^21432991 is an apocalyptic number.

21432991 is a deficient number, since it is larger than the sum of its proper divisors (1).

21432991 is an equidigital number, since it uses as much as digits as its factorization.

21432991 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 3888, while the sum is 31.

The square root of 21432991 is about 4629.5778425252. The cubic root of 21432991 is about 277.7757062897.

The spelling of 21432991 in words is "twenty-one million, four hundred thirty-two thousand, nine hundred ninety-one".