1987126521 has 4 divisors (see below), whose sum is σ = 2649502032. Its totient is φ = 1324751012.

The previous prime is 1987126517. The next prime is 1987126523. The reversal of 1987126521 is 1256217891.

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: 1256217891 = 3 ⋅418739297.

It is a cyclic number.

It is not a de Polignac number, because 1987126521 - 2² = 1987126517 is a prime.

It is not an unprimeable number, because it can be changed into a prime (1987126523) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 331187751 + ... + 331187756.

It is an arithmetic number, because the mean of its divisors is an integer number (662375508).

Almost surely, 2^1987126521 is an apocalyptic number.

It is an amenable number.

1987126521 is a deficient number, since it is larger than the sum of its proper divisors (662375511).

1987126521 is an equidigital number, since it uses as much as digits as its factorization.

1987126521 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 662375510.

The product of its digits is 60480, while the sum is 42.

The square root of 1987126521 is about 44577.1973210519. The cubic root of 1987126521 is about 1257.2119678057.

The spelling of 1987126521 in words is "one billion, nine hundred eighty-seven million, one hundred twenty-six thousand, five hundred twenty-one".