646136021 has 8 divisors (see below), whose sum is σ = 680560320. Its totient is φ = 611753472.

The previous prime is 646136011. The next prime is 646136041. The reversal of 646136021 is 120631646.

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 646136021 - 2⁶ = 646135957 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 (646136011) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 24341 + ... + 43413.

It is an arithmetic number, because the mean of its divisors is an integer number (85070040).

Almost surely, 2^646136021 is an apocalyptic number.

It is an amenable number.

646136021 is a deficient number, since it is larger than the sum of its proper divisors (34424299).

646136021 is a wasteful number, since it uses less digits than its factorization.

646136021 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 20875.

The product of its (nonzero) digits is 5184, while the sum is 29.

The square root of 646136021 is about 25419.2057507704. The cubic root of 646136021 is about 864.5192160418.

Adding to 646136021 its reverse (120631646), we get a palindrome (766767667).

The spelling of 646136021 in words is "six hundred forty-six million, one hundred thirty-six thousand, twenty-one".