21872815 has 8 divisors (see below), whose sum is σ = 27152640. Its totient is φ = 16894752.

The previous prime is 21872801. The next prime is 21872827. The reversal of 21872815 is 51827812.

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 21872815 - 2⁵ = 21872783 is a prime.

It is a congruent number.

It is an unprimeable number.

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, 75279 + ... + 75568.

It is an arithmetic number, because the mean of its divisors is an integer number (3394080).

Almost surely, 2^21872815 is an apocalyptic number.

21872815 is a deficient number, since it is larger than the sum of its proper divisors (5279825).

21872815 is a wasteful number, since it uses less digits than its factorization.

21872815 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 150881.

The product of its digits is 8960, while the sum is 34.

The square root of 21872815 is about 4676.8381413087. The cubic root of 21872815 is about 279.6629234566.

The spelling of 21872815 in words is "twenty-one million, eight hundred seventy-two thousand, eight hundred fifteen".