21297385 has 32 divisors (see below), whose sum is σ = 28344960. Its totient is φ = 15303168.

The previous prime is 21297383. The next prime is 21297431. The reversal of 21297385 is 58379212.

It is a cyclic number.

It is not a de Polignac number, because 21297385 - 2¹ = 21297383 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (37).

It is not an unprimeable number, because it can be changed into a prime (21297383) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 256554 + ... + 256636.

It is an arithmetic number, because the mean of its divisors is an integer number (885780).

Almost surely, 2^21297385 is an apocalyptic number.

It is an amenable number.

21297385 is a deficient number, since it is larger than the sum of its proper divisors (7047575).

21297385 is a wasteful number, since it uses less digits than its factorization.

21297385 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 217.

The product of its digits is 30240, while the sum is 37.

The square root of 21297385 is about 4614.9089915187. The cubic root of 21297385 is about 277.1886397676.

The spelling of 21297385 in words is "twenty-one million, two hundred ninety-seven thousand, three hundred eighty-five".