21715397 has 8 divisors (see below), whose sum is σ = 23727072. Its totient is φ = 19710000.

The previous prime is 21715361. The next prime is 21715433. The reversal of 21715397 is 79351712.

It is a happy number.

It is an interprime number because it is at equal distance from previous prime (21715361) and next prime (21715433).

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 21715397 - 2⁶ = 21715333 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21715327) 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 7 ways as a sum of consecutive naturals, for example, 8522 + ... + 10772.

It is an arithmetic number, because the mean of its divisors is an integer number (2965884).

Almost surely, 2^21715397 is an apocalyptic number.

It is an amenable number.

21715397 is a deficient number, since it is larger than the sum of its proper divisors (2011675).

21715397 is a wasteful number, since it uses less digits than its factorization.

21715397 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3139.

The product of its digits is 13230, while the sum is 35.

The square root of 21715397 is about 4659.9782188332. The cubic root of 21715397 is about 278.9903989022.

The spelling of 21715397 in words is "twenty-one million, seven hundred fifteen thousand, three hundred ninety-seven".