21731533 has 2 divisors, whose sum is σ = 21731534. Its totient is φ = 21731532.

The previous prime is 21731519. The next prime is 21731539. The reversal of 21731533 is 33513712.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 19873764 + 1857769 = 4458^2 + 1363^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21731533 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 21731498 and 21731507.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21731539) 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, 10865766 + 10865767.

It is an arithmetic number, because the mean of its divisors is an integer number (10865767).

Almost surely, 2^21731533 is an apocalyptic number.

It is an amenable number.

21731533 is a deficient number, since it is larger than the sum of its proper divisors (1).

21731533 is an equidigital number, since it uses as much as digits as its factorization.

21731533 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 1890, while the sum is 25.

The square root of 21731533 is about 4661.7092358919. The cubic root of 21731533 is about 279.0594846680.

The spelling of 21731533 in words is "twenty-one million, seven hundred thirty-one thousand, five hundred thirty-three".