1981521567 has 12 divisors (see below), whose sum is σ = 2862720120. Its totient is φ = 1320773328.

The previous prime is 1981521527. The next prime is 1981521611. The reversal of 1981521567 is 7651251891.

1981521567 is a `hidden beast` number, since 1 + 9 + 81 + 5 + 2 + 1 + 567 = 666.

It is not a de Polignac number, because 1981521567 - 2²⁴ = 1964744351 is a prime.

It is a super-2 number, since 2×1981521567² = 7852855440972270978, which contains 22 as substring.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1981521517) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 42109 + ... + 75737.

It is an arithmetic number, because the mean of its divisors is an integer number (238560010).

Almost surely, 2^1981521567 is an apocalyptic number.

1981521567 is a deficient number, since it is larger than the sum of its proper divisors (881198553).

1981521567 is a wasteful number, since it uses less digits than its factorization.

1981521567 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 40182 (or 40179 counting only the distinct ones).

The product of its digits is 151200, while the sum is 45.

The square root of 1981521567 is about 44514.2849768476. The cubic root of 1981521567 is about 1256.0288103034.

The spelling of 1981521567 in words is "one billion, nine hundred eighty-one million, five hundred twenty-one thousand, five hundred sixty-seven".