721666001 has 16 divisors (see below), whose sum is σ = 834113280. Its totient is φ = 611582400.

The previous prime is 721665983. The next prime is 721666013. The reversal of 721666001 is 100666127.

It is a cyclic number.

It is not a de Polignac number, because 721666001 - 2²² = 717471697 is a prime.

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (721666021) 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 15 ways as a sum of consecutive naturals, for example, 554051 + ... + 555351.

It is an arithmetic number, because the mean of its divisors is an integer number (52132080).

Almost surely, 2^721666001 is an apocalyptic number.

It is an amenable number.

721666001 is a deficient number, since it is larger than the sum of its proper divisors (112447279).

721666001 is a wasteful number, since it uses less digits than its factorization.

721666001 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2144.

The product of its (nonzero) digits is 3024, while the sum is 29.

The square root of 721666001 is about 26863.8418883078. The cubic root of 721666001 is about 896.9717153910.

The spelling of 721666001 in words is "seven hundred twenty-one million, six hundred sixty-six thousand, one".