21297697 has 4 divisors (see below), whose sum is σ = 21309316. Its totient is φ = 21286080.

The previous prime is 21297691. The next prime is 21297733. The reversal of 21297697 is 79679212.

It is a semiprime because it is the product of two primes, and also a brilliant number, because the two primes have the same length.

It can be written as a sum of positive squares in 2 ways, for example, as 17172736 + 4124961 = 4144^2 + 2031^2 .

It is a cyclic number.

It is not a de Polignac number, because 21297697 - 2⁷ = 21297569 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21297691) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 2388 + ... + 6949.

It is an arithmetic number, because the mean of its divisors is an integer number (5327329).

Almost surely, 2^21297697 is an apocalyptic number.

It is an amenable number.

21297697 is a deficient number, since it is larger than the sum of its proper divisors (11619).

21297697 is an equidigital number, since it uses as much as digits as its factorization.

21297697 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 11618.

The product of its digits is 95256, while the sum is 43.

The square root of 21297697 is about 4614.9427948784. The cubic root of 21297697 is about 277.1899933365.

The spelling of 21297697 in words is "twenty-one million, two hundred ninety-seven thousand, six hundred ninety-seven".