501981891 has 4 divisors (see below), whose sum is σ = 669309192. Its totient is φ = 334654592.

The previous prime is 501981859. The next prime is 501981911. The reversal of 501981891 is 198189105.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 501981891 - 2⁵ = 501981859 is a prime.

It is not an unprimeable number, because it can be changed into a prime (501981811) 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, 83663646 + ... + 83663651.

It is an arithmetic number, because the mean of its divisors is an integer number (167327298).

Almost surely, 2^501981891 is an apocalyptic number.

501981891 is a deficient number, since it is larger than the sum of its proper divisors (167327301).

501981891 is a wasteful number, since it uses less digits than its factorization.

501981891 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 167327300.

The product of its (nonzero) digits is 25920, while the sum is 42.

The square root of 501981891 is about 22404.9523766510. The cubic root of 501981891 is about 794.7478287267.

The spelling of 501981891 in words is "five hundred one million, nine hundred eighty-one thousand, eight hundred ninety-one".