21398215 has 8 divisors (see below), whose sum is σ = 26506368. Its totient is φ = 16566240.

The previous prime is 21398191. The next prime is 21398227. The reversal of 21398215 is 51289312.

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

It is not a de Polignac number, because 21398215 - 2⁵ = 21398183 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (31).

It is a Duffinian number.

It is a congruent number.

It is an unprimeable number.

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 7 ways as a sum of consecutive naturals, for example, 68872 + ... + 69181.

It is an arithmetic number, because the mean of its divisors is an integer number (3313296).

Almost surely, 2^21398215 is an apocalyptic number.

21398215 is a deficient number, since it is larger than the sum of its proper divisors (5108153).

21398215 is a wasteful number, since it uses less digits than its factorization.

21398215 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 138089.

The product of its digits is 4320, while the sum is 31.

The square root of 21398215 is about 4625.8204677657. The cubic root of 21398215 is about 277.6253904016.

The spelling of 21398215 in words is "twenty-one million, three hundred ninety-eight thousand, two hundred fifteen".