20989847 has 2 divisors, whose sum is σ = 20989848. Its totient is φ = 20989846.

The previous prime is 20989807. The next prime is 20989853. The reversal of 20989847 is 74898902.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 20989847 - 2¹⁰ = 20988823 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (20989807) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10494923 + 10494924.

It is an arithmetic number, because the mean of its divisors is an integer number (10494924).

Almost surely, 2^20989847 is an apocalyptic number.

20989847 is a deficient number, since it is larger than the sum of its proper divisors (1).

20989847 is an equidigital number, since it uses as much as digits as its factorization.

20989847 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 290304, while the sum is 47.

The square root of 20989847 is about 4581.4677779070. The cubic root of 20989847 is about 275.8479479990.

The spelling of 20989847 in words is "twenty million, nine hundred eighty-nine thousand, eight hundred forty-seven".