71636421821 has 4 divisors (see below), whose sum is σ = 71921826144. Its totient is φ = 71351017500.

The previous prime is 71636421817. The next prime is 71636421859. The reversal of 71636421821 is 12812463617.

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: 12812463617 = 227 ⋅56442571.

It is a cyclic number.

It is not a de Polignac number, because 71636421821 - 2² = 71636421817 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (71636421881) 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, 142701785 + ... + 142702286.

It is an arithmetic number, because the mean of its divisors is an integer number (17980456536).

Almost surely, 2^71636421821 is an apocalyptic number.

It is an amenable number.

71636421821 is a deficient number, since it is larger than the sum of its proper divisors (285404323).

71636421821 is a wasteful number, since it uses less digits than its factorization.

71636421821 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 285404322.

The product of its digits is 96768, while the sum is 41.

The spelling of 71636421821 in words is "seventy-one billion, six hundred thirty-six million, four hundred twenty-one thousand, eight hundred twenty-one".