21495217 has 2 divisors, whose sum is σ = 21495218. Its totient is φ = 21495216.

The previous prime is 21495197. The next prime is 21495233. The reversal of 21495217 is 71259412.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 15968016 + 5527201 = 3996^2 + 2351^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21495217 is a prime.

It is not a weakly prime, because it can be changed into another prime (21495277) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10747608 + 10747609.

It is an arithmetic number, because the mean of its divisors is an integer number (10747609).

Almost surely, 2^21495217 is an apocalyptic number.

It is an amenable number.

21495217 is a deficient number, since it is larger than the sum of its proper divisors (1).

21495217 is an equidigital number, since it uses as much as digits as its factorization.

21495217 is an evil number, because the sum of its binary digits is even.

The product of its digits is 5040, while the sum is 31.

The square root of 21495217 is about 4636.2934549055. The cubic root of 21495217 is about 278.0442668842.

It can be divided in two parts, 21495 and 217, that added together give a palindrome (21712).

The spelling of 21495217 in words is "twenty-one million, four hundred ninety-five thousand, two hundred seventeen".