646622721 has 12 divisors (see below), whose sum is σ = 942741072. Its totient is φ = 427052376.

The previous prime is 646622719. The next prime is 646622747. The reversal of 646622721 is 127226646.

646622721 is a `hidden beast` number, since 6 + 4 + 6 + 622 + 7 + 21 = 666.

It is not a de Polignac number, because 646622721 - 2¹ = 646622719 is a prime.

It is not an unprimeable number, because it can be changed into a prime (646622701) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 334771 + ... + 336696.

It is an arithmetic number, because the mean of its divisors is an integer number (78561756).

Almost surely, 2^646622721 is an apocalyptic number.

It is an amenable number.

646622721 is a deficient number, since it is larger than the sum of its proper divisors (296118351).

646622721 is a wasteful number, since it uses less digits than its factorization.

646622721 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 671580 (or 671577 counting only the distinct ones).

The product of its digits is 48384, while the sum is 36.

The square root of 646622721 is about 25428.7774185076. Note that the first 3 decimals coincide. The cubic root of 646622721 is about 864.7362270566.

The spelling of 646622721 in words is "six hundred forty-six million, six hundred twenty-two thousand, seven hundred twenty-one".