20159987 has 4 divisors (see below), whose sum is σ = 20651736. Its totient is φ = 19668240.

The previous prime is 20159957. The next prime is 20160001. The reversal of 20159987 is 78995102.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-20159987 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (41), and also a Moran number because the ratio is a prime number: 491707 = 20159987 / (2 + 0 + 1 + 5 + 9 + 9 + 8 + 7).

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (20159917) 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, 245813 + ... + 245894.

It is an arithmetic number, because the mean of its divisors is an integer number (5162934).

Almost surely, 2^20159987 is an apocalyptic number.

20159987 is a deficient number, since it is larger than the sum of its proper divisors (491749).

20159987 is an equidigital number, since it uses as much as digits as its factorization.

20159987 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 491748.

The product of its (nonzero) digits is 45360, while the sum is 41.

The square root of 20159987 is about 4489.9874164634. The cubic root of 20159987 is about 272.1636261373.

The spelling of 20159987 in words is "twenty million, one hundred fifty-nine thousand, nine hundred eighty-seven".