21428717 has 2 divisors, whose sum is σ = 21428718. Its totient is φ = 21428716.

The previous prime is 21428711. The next prime is 21428731. The reversal of 21428717 is 71782412.

It is a happy number.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 21353641 + 75076 = 4621^2 + 274^2 .

It is a cyclic number.

It is not a de Polignac number, because 21428717 - 2⁸ = 21428461 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21428711) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10714358 + 10714359.

It is an arithmetic number, because the mean of its divisors is an integer number (10714359).

Almost surely, 2^21428717 is an apocalyptic number.

It is an amenable number.

21428717 is a deficient number, since it is larger than the sum of its proper divisors (1).

21428717 is an equidigital number, since it uses as much as digits as its factorization.

21428717 is an evil number, because the sum of its binary digits is even.

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

The square root of 21428717 is about 4629.1162223474. The cubic root of 21428717 is about 277.7572411069.

The spelling of 21428717 in words is "twenty-one million, four hundred twenty-eight thousand, seven hundred seventeen".