21533791 has 2 divisors, whose sum is σ = 21533792. Its totient is φ = 21533790.

The previous prime is 21533789. The next prime is 21533807. The reversal of 21533791 is 19733512.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 21533791 - 2¹ = 21533789 is a prime.

Together with 21533789, 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 (21533711) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10766895 + 10766896.

It is an arithmetic number, because the mean of its divisors is an integer number (10766896).

Almost surely, 2^21533791 is an apocalyptic number.

21533791 is a deficient number, since it is larger than the sum of its proper divisors (1).

21533791 is an equidigital number, since it uses as much as digits as its factorization.

21533791 is an evil number, because the sum of its binary digits is even.

The product of its digits is 5670, while the sum is 31.

The square root of 21533791 is about 4640.4515944033. The cubic root of 21533791 is about 278.2104878982.

The spelling of 21533791 in words is "twenty-one million, five hundred thirty-three thousand, seven hundred ninety-one".