1987651 has 6 divisors (see below), whose sum is σ = 2025452.
Its totient is φ = 1950540.
The previous prime is 1987649. The next prime is 1987673. The reversal of 1987651 is 1567891.
It is not a de Polignac number, because 1987651 - 21 = 1987649 is a prime.
It is a Duffinian number.
Its product of digits (15120) is a multiple of the sum of its prime divisors (630).
It is a self number, because there is not a number n which added to its sum of digits gives 1987651.
It is not an unprimeable number, because it can be changed into a prime (1987621) by changing a digit.
It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 3196 + ... + 3766.
21987651 is an apocalyptic number.
1987651 is the 631-st centered decagonal number.
1987651 is a deficient number, since it is larger than the sum of its proper divisors (37801).
1987651 is an frugal number, since it uses more digits than its factorization.
1987651 is an evil number, because the sum of its binary digits is even.
The sum of its prime factors is 689 (or 630 counting only the distinct ones).
The product of its digits is 15120, while the sum is 37.
The square root of 1987651 is about 1409.8407711511.
The cubic root of 1987651 is about 125.7322566915.
The spelling of 1987651 in words is "one million, nine hundred eighty-seven thousand, six hundred fifty-one".