1987209381 has 4 divisors (see below), whose sum is σ = 2649612512. Its totient is φ = 1324806252.

The previous prime is 1987209331. The next prime is 1987209403. The reversal of 1987209381 is 1839027891.

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.

It is not a de Polignac number, because 1987209381 - 2¹⁴ = 1987192997 is a prime.

It is a super-2 number, since 2×1987209381² = 7898002247868806322, which contains 22 as substring.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 1987209381.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1987209331) 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, 331201561 + ... + 331201566.

It is an arithmetic number, because the mean of its divisors is an integer number (662403128).

Almost surely, 2^1987209381 is an apocalyptic number.

It is an amenable number.

1987209381 is a deficient number, since it is larger than the sum of its proper divisors (662403131).

1987209381 is an equidigital number, since it uses as much as digits as its factorization.

1987209381 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 662403130.

The product of its (nonzero) digits is 217728, while the sum is 48.

The square root of 1987209381 is about 44578.1267103049. The cubic root of 1987209381 is about 1257.2294421394.

The spelling of 1987209381 in words is "one billion, nine hundred eighty-seven million, two hundred nine thousand, three hundred eighty-one".