19915985 has 4 divisors (see below), whose sum is σ = 23899188. Its totient is φ = 15932784.

The previous prime is 19915967. The next prime is 19915991. The reversal of 19915985 is 58951991.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 58951991 = 7 ⋅8421713.

It can be written as a sum of positive squares in 2 ways, for example, as 10137856 + 9778129 = 3184^2 + 3127^2 .

It is a cyclic number.

It is not a de Polignac number, because 19915985 - 2⁸ = 19915729 is a prime.

It is a Duffinian number.

It is a Curzon number.

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 1991594 + ... + 1991603.

It is an arithmetic number, because the mean of its divisors is an integer number (5974797).

Almost surely, 2^19915985 is an apocalyptic number.

It is an amenable number.

19915985 is a deficient number, since it is larger than the sum of its proper divisors (3983203).

19915985 is an equidigital number, since it uses as much as digits as its factorization.

19915985 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3983202.

The product of its digits is 145800, while the sum is 47.

The square root of 19915985 is about 4462.7329070873. The cubic root of 19915985 is about 271.0611418713.

The spelling of 19915985 in words is "nineteen million, nine hundred fifteen thousand, nine hundred eighty-five".