1987855993 has 4 divisors (see below), whose sum is σ = 1998263808. Its totient is φ = 1977448180.

The previous prime is 1987855979. The next prime is 1987856009. The reversal of 1987855993 is 3995587891.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4, and also an emirpimes, since its reverse is a distinct semiprime: 3995587891 = 6947 ⋅575153.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-1987855993 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (1987855973) 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, 5203621 + ... + 5204002.

It is an arithmetic number, because the mean of its divisors is an integer number (499565952).

Almost surely, 2^1987855993 is an apocalyptic number.

It is an amenable number.

1987855993 is a deficient number, since it is larger than the sum of its proper divisors (10407815).

1987855993 is a wasteful number, since it uses less digits than its factorization.

1987855993 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 10407814.

The product of its digits is 24494400, while the sum is 64.

The square root of 1987855993 is about 44585.3786907771. The cubic root of 1987855993 is about 1257.3657893699.

The spelling of 1987855993 in words is "one billion, nine hundred eighty-seven million, eight hundred fifty-five thousand, nine hundred ninety-three".