20985657 has 16 divisors (see below), whose sum is σ = 34885632. Its totient is φ = 10901520.

The previous prime is 20985649. The next prime is 20985703. The reversal of 20985657 is 75658902.

It is not a de Polignac number, because 20985657 - 2³ = 20985649 is a prime.

It is not an unprimeable number, because it can be changed into a prime (20985617) 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 in 15 ways as a sum of consecutive naturals, for example, 45193 + ... + 45654.

It is an arithmetic number, because the mean of its divisors is an integer number (2180352).

Almost surely, 2^20985657 is an apocalyptic number.

It is an amenable number.

20985657 is a deficient number, since it is larger than the sum of its proper divisors (13899975).

20985657 is a wasteful number, since it uses less digits than its factorization.

20985657 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 90868.

The product of its (nonzero) digits is 151200, while the sum is 42.

The square root of 20985657 is about 4581.0104780496. The cubic root of 20985657 is about 275.8295918255.

The spelling of 20985657 in words is "twenty million, nine hundred eighty-five thousand, six hundred fifty-seven".