21935509 has 2 divisors, whose sum is σ = 21935510. Its totient is φ = 21935508.

The previous prime is 21935479. The next prime is 21935527. The reversal of 21935509 is 90553912.

It is a happy number.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 11242609 + 10692900 = 3353^2 + 3270^2 .

It is a cyclic number.

It is not a de Polignac number, because 21935509 - 2²³ = 13546901 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21935549) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10967754 + 10967755.

It is an arithmetic number, because the mean of its divisors is an integer number (10967755).

Almost surely, 2^21935509 is an apocalyptic number.

It is an amenable number.

21935509 is a deficient number, since it is larger than the sum of its proper divisors (1).

21935509 is an equidigital number, since it uses as much as digits as its factorization.

21935509 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 12150, while the sum is 34.

The square root of 21935509 is about 4683.5359505399. The cubic root of 21935509 is about 279.9298676393.

The spelling of 21935509 in words is "twenty-one million, nine hundred thirty-five thousand, five hundred nine".