19661987 has 4 divisors (see below), whose sum is σ = 20516880. Its totient is φ = 18807096.

The previous prime is 19661951. The next prime is 19661989. The reversal of 19661987 is 78916691.

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

It is a cyclic number.

It is not a de Polignac number, because 19661987 - 2⁶ = 19661923 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (19661989) 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, 427412 + ... + 427457.

It is an arithmetic number, because the mean of its divisors is an integer number (5129220).

Almost surely, 2^19661987 is an apocalyptic number.

19661987 is a deficient number, since it is larger than the sum of its proper divisors (854893).

19661987 is an equidigital number, since it uses as much as digits as its factorization.

19661987 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 854892.

The product of its digits is 163296, while the sum is 47.

The square root of 19661987 is about 4434.1839158970. The cubic root of 19661987 is about 269.9038843984.

The spelling of 19661987 in words is "nineteen million, six hundred sixty-one thousand, nine hundred eighty-seven".