21497959 has 4 divisors (see below), whose sum is σ = 24569104. Its totient is φ = 18426816.

The previous prime is 21497953. The next prime is 21497963. The reversal of 21497959 is 95979412.

It is a happy number.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 21497959 - 2⁷ = 21497831 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21497953) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 1535562 + ... + 1535575.

It is an arithmetic number, because the mean of its divisors is an integer number (6142276).

Almost surely, 2^21497959 is an apocalyptic number.

21497959 is a deficient number, since it is larger than the sum of its proper divisors (3071145).

21497959 is an equidigital number, since it uses as much as digits as its factorization.

21497959 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3071144.

The product of its digits is 204120, while the sum is 46.

The square root of 21497959 is about 4636.5891558343. The cubic root of 21497959 is about 278.0560891261.

The spelling of 21497959 in words is "twenty-one million, four hundred ninety-seven thousand, nine hundred fifty-nine".