1987557891 has 32 divisors (see below), whose sum is σ = 3020440320. Its totient is φ = 1151472000.

The previous prime is 1987557889. The next prime is 1987557917.

It is a happy number.

1987557891 is nontrivially palindromic in base 10.

It is not a de Polignac number, because 1987557891 - 2¹ = 1987557889 is a prime.

It is not an unprimeable number, because it can be changed into a prime (1987557821) by changing a digit.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 86376 + ... + 106938.

It is an arithmetic number, because the mean of its divisors is an integer number (94388760).

Almost surely, 2^1987557891 is an apocalyptic number.

1987557891 is a gapful number since it is divisible by the number (11) formed by its first and last digit.

1987557891 is a deficient number, since it is larger than the sum of its proper divisors (1032882429).

1987557891 is a wasteful number, since it uses less digits than its factorization.

1987557891 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 20707.

The product of its digits is 6350400, while the sum is 60.

The square root of 1987557891 is about 44582.0355188051. The cubic root of 1987557891 is about 1257.3029340464.

The spelling of 1987557891 in words is "one billion, nine hundred eighty-seven million, five hundred fifty-seven thousand, eight hundred ninety-one".