19978985 has 16 divisors (see below), whose sum is σ = 25919040. Its totient is φ = 14696640.

The previous prime is 19978979. The next prime is 19978991. The reversal of 19978985 is 58987991.

It is a happy number.

It is an interprime number because it is at equal distance from previous prime (19978979) and next prime (19978991).

It is not a de Polignac number, because 19978985 - 2⁶ = 19978921 is a prime.

It is a Curzon number.

It is a self number, because there is not a number n which added to its sum of digits gives 19978985.

It is an unprimeable number.

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 in 15 ways as a sum of consecutive naturals, for example, 24230 + ... + 25040.

It is an arithmetic number, because the mean of its divisors is an integer number (1619940).

Almost surely, 2^19978985 is an apocalyptic number.

It is an amenable number.

19978985 is a deficient number, since it is larger than the sum of its proper divisors (5940055).

19978985 is a wasteful number, since it uses less digits than its factorization.

19978985 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1208.

The product of its digits is 1632960, while the sum is 56.

The square root of 19978985 is about 4469.7857890507. The cubic root of 19978985 is about 271.3466558639.

It can be divided in two parts, 1997 and 8985, that multiplied together give a triangular number (17943045 = T₅₉₉₀).

The spelling of 19978985 in words is "nineteen million, nine hundred seventy-eight thousand, nine hundred eighty-five".