3891216521 has 8 divisors (see below), whose sum is σ = 4078292544. Its totient is φ = 3705631600.

The previous prime is 3891216517. The next prime is 3891216523. The reversal of 3891216521 is 1256121983.

It is a happy number.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 3891216521 - 2² = 3891216517 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (3891216523) 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 7 ways as a sum of consecutive naturals, for example, 367430 + ... + 377871.

It is an arithmetic number, because the mean of its divisors is an integer number (509786568).

Almost surely, 2^3891216521 is an apocalyptic number.

It is an amenable number.

3891216521 is a deficient number, since it is larger than the sum of its proper divisors (187076023).

3891216521 is a wasteful number, since it uses less digits than its factorization.

3891216521 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 745551.

The product of its digits is 25920, while the sum is 38.

The square root of 3891216521 is about 62379.6162299833. The cubic root of 3891216521 is about 1572.8783419879.

The spelling of 3891216521 in words is "three billion, eight hundred ninety-one million, two hundred sixteen thousand, five hundred twenty-one".