20987579 has 2 divisors, whose sum is σ = 20987580. Its totient is φ = 20987578.

The previous prime is 20987557. The next prime is 20987581. The reversal of 20987579 is 97578902.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 20987579 - 2¹⁶ = 20922043 is a prime.

Together with 20987581, it forms a pair of twin primes.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (20987479) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10493789 + 10493790.

It is an arithmetic number, because the mean of its divisors is an integer number (10493790).

Almost surely, 2^20987579 is an apocalyptic number.

20987579 is a deficient number, since it is larger than the sum of its proper divisors (1).

20987579 is an equidigital number, since it uses as much as digits as its factorization.

20987579 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 317520, while the sum is 47.

The square root of 20987579 is about 4581.2202522909. The cubic root of 20987579 is about 275.8380123115.

The spelling of 20987579 in words is "twenty million, nine hundred eighty-seven thousand, five hundred seventy-nine".