21489917 has 2 divisors, whose sum is σ = 21489918. Its totient is φ = 21489916.

The previous prime is 21489911. The next prime is 21489943. The reversal of 21489917 is 71998412.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 11383876 + 10106041 = 3374^2 + 3179^2 .

It is a cyclic number.

It is not a de Polignac number, because 21489917 - 2⁴ = 21489901 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 (21489911) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10744958 + 10744959.

It is an arithmetic number, because the mean of its divisors is an integer number (10744959).

Almost surely, 2^21489917 is an apocalyptic number.

It is an amenable number.

21489917 is a deficient number, since it is larger than the sum of its proper divisors (1).

21489917 is an equidigital number, since it uses as much as digits as its factorization.

21489917 is an evil number, because the sum of its binary digits is even.

The product of its digits is 36288, while the sum is 41.

The square root of 21489917 is about 4635.7218423887. The cubic root of 21489917 is about 278.0214128737.

The spelling of 21489917 in words is "twenty-one million, four hundred eighty-nine thousand, nine hundred seventeen".