21064247 has 2 divisors, whose sum is σ = 21064248. Its totient is φ = 21064246.

The previous prime is 21064231. The next prime is 21064249. The reversal of 21064247 is 74246012.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 21064247 - 2⁴ = 21064231 is a prime.

Together with 21064249, it forms a pair of twin primes.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21064249) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10532123 + 10532124.

It is an arithmetic number, because the mean of its divisors is an integer number (10532124).

Almost surely, 2^21064247 is an apocalyptic number.

21064247 is a deficient number, since it is larger than the sum of its proper divisors (1).

21064247 is an equidigital number, since it uses as much as digits as its factorization.

21064247 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 2688, while the sum is 26.

The square root of 21064247 is about 4589.5802640329. The cubic root of 21064247 is about 276.1734845383.

The spelling of 21064247 in words is "twenty-one million, sixty-four thousand, two hundred forty-seven".