721475666 has 4 divisors (see below), whose sum is σ = 1082213502. Its totient is φ = 360737832.

The previous prime is 721475639. The next prime is 721475669. The reversal of 721475666 is 666574127.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in only one way, i.e., 571927225 + 149548441 = 23915^2 + 12229^2 .

It is not an unprimeable number, because it can be changed into a prime (721475669) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 180368915 + ... + 180368918.

Almost surely, 2^721475666 is an apocalyptic number.

721475666 is a deficient number, since it is larger than the sum of its proper divisors (360737836).

721475666 is a wasteful number, since it uses less digits than its factorization.

721475666 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 360737835.

The product of its digits is 423360, while the sum is 44.

The square root of 721475666 is about 26860.2990675830. The cubic root of 721475666 is about 896.8928515202.

The spelling of 721475666 in words is "seven hundred twenty-one million, four hundred seventy-five thousand, six hundred sixty-six".