21297973 has 2 divisors, whose sum is σ = 21297974. Its totient is φ = 21297972.

The previous prime is 21297953. The next prime is 21297979. The reversal of 21297973 is 37979212.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 20958084 + 339889 = 4578^2 + 583^2 .

It is a cyclic number.

It is not a de Polignac number, because 21297973 - 2¹³ = 21289781 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21297979) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10648986 + 10648987.

It is an arithmetic number, because the mean of its divisors is an integer number (10648987).

Almost surely, 2^21297973 is an apocalyptic number.

It is an amenable number.

21297973 is a deficient number, since it is larger than the sum of its proper divisors (1).

21297973 is an equidigital number, since it uses as much as digits as its factorization.

21297973 is an evil number, because the sum of its binary digits is even.

The product of its digits is 47628, while the sum is 40.

The square root of 21297973 is about 4614.9726976440. The cubic root of 21297973 is about 277.1911907133.

The spelling of 21297973 in words is "twenty-one million, two hundred ninety-seven thousand, nine hundred seventy-three".