721769 has 4 divisors (see below), whose sum is σ = 764244. Its totient is φ = 679296.

The previous prime is 721739. The next prime is 721783. The reversal of 721769 is 967127.

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

It can be written as a sum of positive squares in 2 ways, for example, as 619369 + 102400 = 787^2 + 320^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-721769 is a prime.

It is a super-2 number, since 2×721769² = 1041900978722, which contains 22 as substring.

It is a Duffinian number.

It is an inconsummate number, since it does not exist a number n which divided by its sum of digits gives 721769.

It is not an unprimeable number, because it can be changed into a prime (721709) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 21212 + ... + 21245.

It is an arithmetic number, because the mean of its divisors is an integer number (191061).

2⁷²¹⁷⁶⁹ is an apocalyptic number.

It is an amenable number.

721769 is a deficient number, since it is larger than the sum of its proper divisors (42475).

721769 is a wasteful number, since it uses less digits than its factorization.

721769 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 42474.

The product of its digits is 5292, while the sum is 32.

The square root of 721769 is about 849.5698911802. The cubic root of 721769 is about 89.7014386467.

Adding to 721769 its sum of digits (32), we get a triangular number (721801 = T₁₂₀₁).

The spelling of 721769 in words is "seven hundred twenty-one thousand, seven hundred sixty-nine".