21429817 has 2 divisors, whose sum is σ = 21429818. Its totient is φ = 21429816.

The previous prime is 21429799. The next prime is 21429827. The reversal of 21429817 is 71892412.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 21353641 + 76176 = 4621^2 + 276^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21429817 is a prime.

It is not a weakly prime, because it can be changed into another prime (21429827) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10714908 + 10714909.

It is an arithmetic number, because the mean of its divisors is an integer number (10714909).

Almost surely, 2^21429817 is an apocalyptic number.

It is an amenable number.

21429817 is a deficient number, since it is larger than the sum of its proper divisors (1).

21429817 is an equidigital number, since it uses as much as digits as its factorization.

21429817 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 8064, while the sum is 34.

The square root of 21429817 is about 4629.2350339986. The cubic root of 21429817 is about 277.7619937283.

The spelling of 21429817 in words is "twenty-one million, four hundred twenty-nine thousand, eight hundred seventeen".