723687821 has 4 divisors (see below), whose sum is σ = 730092252. Its totient is φ = 717283392.

The previous prime is 723687817. The next prime is 723687823. The reversal of 723687821 is 128786327.

It is a happy number.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 128786327 = 2237 ⋅57571.

It can be written as a sum of positive squares in 2 ways, for example, as 147015625 + 576672196 = 12125^2 + 24014^2 .

It is a cyclic number.

It is not a de Polignac number, because 723687821 - 2² = 723687817 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (723687823) 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, 3202046 + ... + 3202271.

It is an arithmetic number, because the mean of its divisors is an integer number (182523063).

Almost surely, 2^723687821 is an apocalyptic number.

It is an amenable number.

723687821 is a deficient number, since it is larger than the sum of its proper divisors (6404431).

723687821 is a wasteful number, since it uses less digits than its factorization.

723687821 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 6404430.

The product of its digits is 225792, while the sum is 44.

The square root of 723687821 is about 26901.4464481001. The cubic root of 723687821 is about 897.8085865568.

The spelling of 723687821 in words is "seven hundred twenty-three million, six hundred eighty-seven thousand, eight hundred twenty-one".