21428915 has 4 divisors (see below), whose sum is σ = 25714704. Its totient is φ = 17143128.

The previous prime is 21428909. The next prime is 21428923. The reversal of 21428915 is 51982412.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 21428915 - 2¹⁰ = 21427891 is a prime.

It is a Duffinian number.

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 2142887 + ... + 2142896.

It is an arithmetic number, because the mean of its divisors is an integer number (6428676).

Almost surely, 2^21428915 is an apocalyptic number.

21428915 is a deficient number, since it is larger than the sum of its proper divisors (4285789).

21428915 is an equidigital number, since it uses as much as digits as its factorization.

21428915 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 4285788.

The product of its digits is 5760, while the sum is 32.

The square root of 21428915 is about 4629.1376086697. The cubic root of 21428915 is about 277.7580965908.

The spelling of 21428915 in words is "twenty-one million, four hundred twenty-eight thousand, nine hundred fifteen".