17428721 has 4 divisors (see below), whose sum is σ = 17444592. Its totient is φ = 17412852.

The previous prime is 17428673. The next prime is 17428753. The reversal of 17428721 is 12782471.

It is a happy number.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4, and also an emirpimes, since its reverse is a distinct semiprime: 12782471 = 13 ⋅983267.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-17428721 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (17428771) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 6155 + ... + 8528.

It is an arithmetic number, because the mean of its divisors is an integer number (4361148).

Almost surely, 2^17428721 is an apocalyptic number.

It is an amenable number.

17428721 is a deficient number, since it is larger than the sum of its proper divisors (15871).

17428721 is a wasteful number, since it uses less digits than its factorization.

17428721 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 15870.

The product of its digits is 6272, while the sum is 32.

The square root of 17428721 is about 4174.7719698206. The cubic root of 17428721 is about 259.2717342052.

The spelling of 17428721 in words is "seventeen million, four hundred twenty-eight thousand, seven hundred twenty-one".