17728421 has 2 divisors, whose sum is σ = 17728422. Its totient is φ = 17728420.

The previous prime is 17728411. The next prime is 17728453. The reversal of 17728421 is 12482771.

It is a happy number.

It is an a-pointer prime, because the next prime (17728453) can be obtained adding 17728421 to its sum of digits (32).

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 16900321 + 828100 = 4111^2 + 910^2 .

It is a cyclic number.

It is not a de Polignac number, because 17728421 - 2⁶ = 17728357 is a prime.

It is a super-2 number, since 2×17728421² = 628593822306482, which contains 22 as substring.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (17728411) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 8864210 + 8864211.

It is an arithmetic number, because the mean of its divisors is an integer number (8864211).

Almost surely, 2^17728421 is an apocalyptic number.

It is an amenable number.

17728421 is a deficient number, since it is larger than the sum of its proper divisors (1).

17728421 is an equidigital number, since it uses as much as digits as its factorization.

17728421 is an odious number, because the sum of its binary digits is odd.

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

The square root of 17728421 is about 4210.5131516242. The cubic root of 17728421 is about 260.7494206444.

The spelling of 17728421 in words is "seventeen million, seven hundred twenty-eight thousand, four hundred twenty-one".