721655 has 8 divisors (see below), whose sum is σ = 944784. Its totient is φ = 524800.

The previous prime is 721631. The next prime is 721661. The reversal of 721655 is 556127.

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

It is not a de Polignac number, because 721655 - 2¹² = 717559 is a prime.

It is a super-3 number, since 3×721655³ = 1127483330481259125, which contains 333 as substring.

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 721655.

It is an unprimeable number.

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 in 7 ways as a sum of consecutive naturals, for example, 6506 + ... + 6615.

It is an arithmetic number, because the mean of its divisors is an integer number (118098).

2⁷²¹⁶⁵⁵ is an apocalyptic number.

721655 is a deficient number, since it is larger than the sum of its proper divisors (223129).

721655 is a wasteful number, since it uses less digits than its factorization.

721655 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 13137.

The product of its digits is 2100, while the sum is 26.

The square root of 721655 is about 849.5027957576. The cubic root of 721655 is about 89.6967157587.

It can be divided in two parts, 72165 and 5, that multiplied together give a triangular number (360825 = T₈₄₉).

The spelling of 721655 in words is "seven hundred twenty-one thousand, six hundred fifty-five".