721641 has 8 divisors (see below), whose sum is σ = 985824. Its totient is φ = 469280.

The previous prime is 721631. The next prime is 721661. The reversal of 721641 is 146127.

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

It is a cyclic number.

It is not a de Polignac number, because 721641 - 2⁶ = 721577 is a prime.

It is an inconsummate number, since it does not exist a number n which divided by its sum of digits gives 721641.

It is not an unprimeable number, because it can be changed into a prime (721621) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 2811 + ... + 3056.

It is an arithmetic number, because the mean of its divisors is an integer number (123228).

2⁷²¹⁶⁴¹ is an apocalyptic number.

It is an amenable number.

721641 is a deficient number, since it is larger than the sum of its proper divisors (264183).

721641 is a wasteful number, since it uses less digits than its factorization.

721641 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 5911.

The product of its digits is 336, while the sum is 21.

The square root of 721641 is about 849.4945556035. The cubic root of 721641 is about 89.6961357206.

Adding to 721641 its reverse (146127), we get a palindrome (867768).

The spelling of 721641 in words is "seven hundred twenty-one thousand, six hundred forty-one".