100021987 has 4 divisors (see below), whose sum is σ = 107716000. Its totient is φ = 92327976.

The previous prime is 100021981. The next prime is 100021993. The reversal of 100021987 is 789120001.

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

It is an interprime number because it is at equal distance from previous prime (100021981) and next prime (100021993).

It is a de Polignac number, because none of the positive numbers 2^k-100021987 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (100021981) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 3846987 + ... + 3847012.

It is an arithmetic number, because the mean of its divisors is an integer number (26929000).

Almost surely, 2^100021987 is an apocalyptic number.

100021987 is a deficient number, since it is larger than the sum of its proper divisors (7694013).

100021987 is an equidigital number, since it uses as much as digits as its factorization.

100021987 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 7694012.

The product of its (nonzero) digits is 1008, while the sum is 28.

The square root of 100021987 is about 10001.0992895781. The cubic root of 100021987 is about 464.1928990729.

Adding to 100021987 its reverse (789120001), we get a palindrome (889141988).

The spelling of 100021987 in words is "one hundred million, twenty-one thousand, nine hundred eighty-seven".