623721 has 12 divisors (see below), whose sum is σ = 967632. Its totient is φ = 356328.

The previous prime is 623719. The next prime is 623723. The reversal of 623721 is 127326.

It is a happy number.

It is an interprime number because it is at equal distance from previous prime (623719) and next prime (623723).

It is not a de Polignac number, because 623721 - 2¹ = 623719 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (21).

623721 is a lucky number.

It is not an unprimeable number, because it can be changed into a prime (623723) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 1975 + ... + 2268.

It is an arithmetic number, because the mean of its divisors is an integer number (80636).

2⁶²³⁷²¹ is an apocalyptic number.

It is an amenable number.

623721 is a deficient number, since it is larger than the sum of its proper divisors (343911).

623721 is a wasteful number, since it uses less digits than its factorization.

623721 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4260 (or 4253 counting only the distinct ones).

The product of its digits is 504, while the sum is 21.

The square root of 623721 is about 789.7600901540. The cubic root of 623721 is about 85.4404359258.

The spelling of 623721 in words is "six hundred twenty-three thousand, seven hundred twenty-one".