721669 has 8 divisors (see below), whose sum is σ = 795872. Its totient is φ = 650160.

The previous prime is 721663. The next prime is 721687. The reversal of 721669 is 966127.

It is a sphenic number, since it is the product of 3 distinct primes.

It is not a de Polignac number, because 721669 - 2³ = 721661 is a prime.

It is a super-2 number, since 2×721669² = 1041612291122, which contains 22 as substring.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 721669.

It is a congruent number.

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 7 ways as a sum of consecutive naturals, for example, 87 + ... + 1204.

It is an arithmetic number, because the mean of its divisors is an integer number (99484).

2⁷²¹⁶⁶⁹ is an apocalyptic number.

It is an amenable number.

721669 is a deficient number, since it is larger than the sum of its proper divisors (74203).

721669 is a wasteful number, since it uses less digits than its factorization.

721669 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1347.

The product of its digits is 4536, while the sum is 31.

The square root of 721669 is about 849.5110358318. The cubic root of 721669 is about 89.6972957893.

The spelling of 721669 in words is "seven hundred twenty-one thousand, six hundred sixty-nine".