19887978 has 16 divisors (see below), whose sum is σ = 43392096. Its totient is φ = 6026640.

The previous prime is 19887971. The next prime is 19887979. The reversal of 19887978 is 87978891.

It is not an unprimeable number, because it can be changed into a prime (19887971) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 150601 + ... + 150732.

It is an arithmetic number, because the mean of its divisors is an integer number (2712006).

Almost surely, 2^19887978 is an apocalyptic number.

19887978 is an abundant number, since it is smaller than the sum of its proper divisors (23504118).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

19887978 is a wasteful number, since it uses less digits than its factorization.

19887978 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 301349.

The product of its digits is 2032128, while the sum is 57.

The square root of 19887978 is about 4459.5939277024. The cubic root of 19887978 is about 270.9340216917.

The spelling of 19887978 in words is "nineteen million, eight hundred eighty-seven thousand, nine hundred seventy-eight".