20993857 has 2 divisors, whose sum is σ = 20993858. Its totient is φ = 20993856.

The previous prime is 20993839. The next prime is 20993873. The reversal of 20993857 is 75839902.

It is a happy number.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 16289296 + 4704561 = 4036^2 + 2169^2 .

It is a cyclic number.

It is not a de Polignac number, because 20993857 - 2¹¹ = 20991809 is a prime.

It is not a weakly prime, because it can be changed into another prime (20993897) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10496928 + 10496929.

It is an arithmetic number, because the mean of its divisors is an integer number (10496929).

Almost surely, 2^20993857 is an apocalyptic number.

It is an amenable number.

20993857 is a deficient number, since it is larger than the sum of its proper divisors (1).

20993857 is an equidigital number, since it uses as much as digits as its factorization.

20993857 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 136080, while the sum is 43.

The square root of 20993857 is about 4581.9053896823. The cubic root of 20993857 is about 275.8655133142.

It can be divided in two parts, 20993 and 857, that multiplied together give a triangular number (17991001 = T₅₉₉₈).

The spelling of 20993857 in words is "twenty million, nine hundred ninety-three thousand, eight hundred fifty-seven".