646552421 has 4 divisors (see below), whose sum is σ = 646613100. Its totient is φ = 646491744.

The previous prime is 646552391. The next prime is 646552441. The reversal of 646552421 is 124255646.

646552421 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a semiprime because it is the product of two primes, and also a brilliant number, because the two primes have the same length, and also an emirpimes, since its reverse is a distinct semiprime: 124255646 = 2 ⋅62127823.

It can be written as a sum of positive squares in 2 ways, for example, as 509404900 + 137147521 = 22570^2 + 11711^2 .

It is a cyclic number.

It is not a de Polignac number, because 646552421 - 2²² = 642358117 is a prime.

It is a super-2 number, since 2×646552421² = 836060066201922482, which contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (646552441) 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, 9656 + ... + 37233.

It is an arithmetic number, because the mean of its divisors is an integer number (161653275).

Almost surely, 2^646552421 is an apocalyptic number.

It is an amenable number.

646552421 is a deficient number, since it is larger than the sum of its proper divisors (60679).

646552421 is a wasteful number, since it uses less digits than its factorization.

646552421 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 60678.

The product of its digits is 57600, while the sum is 35.

The square root of 646552421 is about 25427.3950887620. The cubic root of 646552421 is about 864.7048882465.

It can be divided in two parts, 64655 and 2421, that added together give a palindrome (67076).

The spelling of 646552421 in words is "six hundred forty-six million, five hundred fifty-two thousand, four hundred twenty-one".