19138987 has 4 divisors (see below), whose sum is σ = 21873136. Its totient is φ = 16404840.

The previous prime is 19138979. The next prime is 19138993. The reversal of 19138987 is 78983191.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 78983191 = 7 ⋅11283313.

It is a cyclic number.

It is not a de Polignac number, because 19138987 - 2³ = 19138979 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (19138087) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 1367064 + ... + 1367077.

It is an arithmetic number, because the mean of its divisors is an integer number (5468284).

Almost surely, 2^19138987 is an apocalyptic number.

19138987 is a deficient number, since it is larger than the sum of its proper divisors (2734149).

19138987 is an equidigital number, since it uses as much as digits as its factorization.

19138987 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2734148.

The product of its digits is 108864, while the sum is 46.

The square root of 19138987 is about 4374.8127959948. The cubic root of 19138987 is about 267.4892393843.

The spelling of 19138987 in words is "nineteen million, one hundred thirty-eight thousand, nine hundred eighty-seven".