646213621 has 8 divisors (see below), whose sum is σ = 667352504. Its totient is φ = 625268160.

The previous prime is 646213619. The next prime is 646213627. The reversal of 646213621 is 126312646.

It can be written as a sum of positive squares in 4 ways, for example, as 4351396 + 641862225 = 2086^2 + 25335^2 .

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 646213621 - 2¹ = 646213619 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 (646213627) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 41550 + ... + 54943.

It is an arithmetic number, because the mean of its divisors is an integer number (83419063).

Almost surely, 2^646213621 is an apocalyptic number.

It is an amenable number.

646213621 is a deficient number, since it is larger than the sum of its proper divisors (21138883).

646213621 is a wasteful number, since it uses less digits than its factorization.

646213621 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 96711.

The product of its digits is 10368, while the sum is 31.

The square root of 646213621 is about 25420.7321098351. The cubic root of 646213621 is about 864.5538238248.

The spelling of 646213621 in words is "six hundred forty-six million, two hundred thirteen thousand, six hundred twenty-one".