21028915 has 32 divisors (see below), whose sum is σ = 29160000. Its totient is φ = 14450688.

The previous prime is 21028901. The next prime is 21028919. The reversal of 21028915 is 51982012.

21028915 = 448² + 449² + ... + 534².

It is a cyclic number.

It is not a de Polignac number, because 21028915 - 2⁵ = 21028883 is a prime.

It is not an unprimeable number, because it can be changed into a prime (21028919) by changing a digit.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 46611 + ... + 47059.

It is an arithmetic number, because the mean of its divisors is an integer number (911250).

Almost surely, 2^21028915 is an apocalyptic number.

21028915 is a deficient number, since it is larger than the sum of its proper divisors (8131085).

21028915 is a wasteful number, since it uses less digits than its factorization.

21028915 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 519.

The product of its (nonzero) digits is 1440, while the sum is 28.

The square root of 21028915 is about 4585.7294948568. The cubic root of 21028915 is about 276.0189854265.

The spelling of 21028915 in words is "twenty-one million, twenty-eight thousand, nine hundred fifteen".