21147517 has 2 divisors, whose sum is σ = 21147518. Its totient is φ = 21147516.

The previous prime is 21147499. The next prime is 21147523. The reversal of 21147517 is 71574112.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 18071001 + 3076516 = 4251^2 + 1754^2 .

It is a cyclic number.

It is not a de Polignac number, because 21147517 - 2⁷ = 21147389 is a prime.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21147317) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10573758 + 10573759.

It is an arithmetic number, because the mean of its divisors is an integer number (10573759).

Almost surely, 2^21147517 is an apocalyptic number.

It is an amenable number.

21147517 is a deficient number, since it is larger than the sum of its proper divisors (1).

21147517 is an equidigital number, since it uses as much as digits as its factorization.

21147517 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 1960, while the sum is 28.

The square root of 21147517 is about 4598.6429520023. The cubic root of 21147517 is about 276.5369238927.

The spelling of 21147517 in words is "twenty-one million, one hundred forty-seven thousand, five hundred seventeen".