721667 has 4 divisors (see below), whose sum is σ = 764136. Its totient is φ = 679200.

The previous prime is 721663. The next prime is 721687. The reversal of 721667 is 766127.

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

It is a cyclic number.

It is not a de Polignac number, because 721667 - 2² = 721663 is a prime.

It is a Duffinian number.

It is a congruent number.

It is an inconsummate number, since it does not exist a number n which divided by its sum of digits gives 721667.

It is not an unprimeable number, because it can be changed into a prime (721661) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (7) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 21209 + ... + 21242.

It is an arithmetic number, because the mean of its divisors is an integer number (191034).

2⁷²¹⁶⁶⁷ is an apocalyptic number.

721667 is a deficient number, since it is larger than the sum of its proper divisors (42469).

721667 is a wasteful number, since it uses less digits than its factorization.

721667 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 42468.

The product of its digits is 3528, while the sum is 29.

The square root of 721667 is about 849.5098586832. The cubic root of 721667 is about 89.6972129283.

The spelling of 721667 in words is "seven hundred twenty-one thousand, six hundred sixty-seven".