20917847 has 2 divisors, whose sum is σ = 20917848. Its totient is φ = 20917846.

The previous prime is 20917843. The next prime is 20917849. The reversal of 20917847 is 74871902.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 20917847 - 2² = 20917843 is a prime.

Together with 20917849, it forms a pair of twin primes.

It is a Chen prime.

It is a self number, because there is not a number n which added to its sum of digits gives 20917847.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (20917843) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10458923 + 10458924.

It is an arithmetic number, because the mean of its divisors is an integer number (10458924).

Almost surely, 2^20917847 is an apocalyptic number.

20917847 is a deficient number, since it is larger than the sum of its proper divisors (1).

20917847 is an equidigital number, since it uses as much as digits as its factorization.

20917847 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 28224, while the sum is 38.

The square root of 20917847 is about 4573.6032840639. The cubic root of 20917847 is about 275.5321793807.

The spelling of 20917847 in words is "twenty million, nine hundred seventeen thousand, eight hundred forty-seven".