21897215 has 16 divisors (see below), whose sum is σ = 28188000. Its totient is φ = 16278912.

The previous prime is 21897193. The next prime is 21897223. The reversal of 21897215 is 51279812.

It is a cyclic number.

It is not a de Polignac number, because 21897215 - 2⁶ = 21897151 is a prime.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 2861 + ... + 7209.

It is an arithmetic number, because the mean of its divisors is an integer number (1761750).

Almost surely, 2^21897215 is an apocalyptic number.

21897215 is a deficient number, since it is larger than the sum of its proper divisors (6290785).

21897215 is a wasteful number, since it uses less digits than its factorization.

21897215 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4426.

The product of its digits is 10080, while the sum is 35.

The square root of 21897215 is about 4679.4460142201. The cubic root of 21897215 is about 279.7668765373.

The spelling of 21897215 in words is "twenty-one million, eight hundred ninety-seven thousand, two hundred fifteen".