21428715 has 32 divisors (see below), whose sum is σ = 42748416. Its totient is φ = 8904960.

The previous prime is 21428711. The next prime is 21428717. The reversal of 21428715 is 51782412.

It is not a de Polignac number, because 21428715 - 2² = 21428711 is a prime.

It is not an unprimeable number, because it can be changed into a prime (21428711) 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, 8122 + ... + 10431.

It is an arithmetic number, because the mean of its divisors is an integer number (1335888).

Almost surely, 2^21428715 is an apocalyptic number.

21428715 is a deficient number, since it is larger than the sum of its proper divisors (21319701).

21428715 is a wasteful number, since it uses less digits than its factorization.

21428715 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 18579.

The product of its digits is 4480, while the sum is 30.

The square root of 21428715 is about 4629.1160063235. The cubic root of 21428715 is about 277.7572324656.

The spelling of 21428715 in words is "twenty-one million, four hundred twenty-eight thousand, seven hundred fifteen".