646143821 has 4 divisors (see below), whose sum is σ = 648248832. Its totient is φ = 644038812.

The previous prime is 646143793. The next prime is 646143859. The reversal of 646143821 is 128341646.

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.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-646143821 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 (646143521) 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, 1052045 + ... + 1052658.

It is an arithmetic number, because the mean of its divisors is an integer number (162062208).

Almost surely, 2^646143821 is an apocalyptic number.

It is an amenable number.

646143821 is a deficient number, since it is larger than the sum of its proper divisors (2105011).

646143821 is a wasteful number, since it uses less digits than its factorization.

646143821 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2105010.

The product of its digits is 27648, while the sum is 35.

The square root of 646143821 is about 25419.3591776032. The cubic root of 646143821 is about 864.5226947844.

The spelling of 646143821 in words is "six hundred forty-six million, one hundred forty-three thousand, eight hundred twenty-one".