28415721 has 16 divisors (see below), whose sum is σ = 40224384. Its totient is φ = 17781504.

The previous prime is 28415707. The next prime is 28415749. The reversal of 28415721 is 12751482.

It is not a de Polignac number, because 28415721 - 2⁶ = 28415657 is a prime.

It is not an unprimeable number, because it can be changed into a prime (28415701) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 34116 + ... + 34938.

It is an arithmetic number, because the mean of its divisors is an integer number (2514024).

Almost surely, 2^28415721 is an apocalyptic number.

It is an amenable number.

28415721 is a deficient number, since it is larger than the sum of its proper divisors (11808663).

28415721 is a wasteful number, since it uses less digits than its factorization.

28415721 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1520.

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

The square root of 28415721 is about 5330.6398302643. The cubic root of 28415721 is about 305.1543463172.

The spelling of 28415721 in words is "twenty-eight million, four hundred fifteen thousand, seven hundred twenty-one".