8021216391 has 4 divisors (see below), whose sum is σ = 10694955192. Its totient is φ = 5347477592.

The previous prime is 8021216389. The next prime is 8021216419. The reversal of 8021216391 is 1936121208.

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 8021216391 - 2¹ = 8021216389 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (8021216341) 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, 1336869396 + ... + 1336869401.

It is an arithmetic number, because the mean of its divisors is an integer number (2673738798).

Almost surely, 2^8021216391 is an apocalyptic number.

8021216391 is a deficient number, since it is larger than the sum of its proper divisors (2673738801).

8021216391 is a wasteful number, since it uses less digits than its factorization.

8021216391 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2673738800.

The product of its (nonzero) digits is 5184, while the sum is 33.

The square root of 8021216391 is about 89561.2437999830. The cubic root of 8021216391 is about 2001.7664719125.

Adding to 8021216391 its reverse (1936121208), we get a palindrome (9957337599).

The spelling of 8021216391 in words is "eight billion, twenty-one million, two hundred sixteen thousand, three hundred ninety-one".