21047647 has 2 divisors, whose sum is σ = 21047648. Its totient is φ = 21047646.

The previous prime is 21047629. The next prime is 21047657. The reversal of 21047647 is 74674012.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 21047647 - 2¹¹ = 21045599 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21047617) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10523823 + 10523824.

It is an arithmetic number, because the mean of its divisors is an integer number (10523824).

Almost surely, 2^21047647 is an apocalyptic number.

21047647 is a deficient number, since it is larger than the sum of its proper divisors (1).

21047647 is an equidigital number, since it uses as much as digits as its factorization.

21047647 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 9408, while the sum is 31.

The square root of 21047647 is about 4587.7714633578. The cubic root of 21047647 is about 276.1009179018.

The spelling of 21047647 in words is "twenty-one million, forty-seven thousand, six hundred forty-seven".