721109381 has 4 divisors (see below), whose sum is σ = 723384492. Its totient is φ = 718834272.

The previous prime is 721109377. The next prime is 721109401. The reversal of 721109381 is 183901127.

721109381 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

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 433264225 + 287845156 = 20815^2 + 16966^2 .

It is not a de Polignac number, because 721109381 - 2² = 721109377 is a prime.

It is a super-2 number, since 2×721109381² = 1039997478732406322, which contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (721109341) 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, 1137080 + ... + 1137713.

It is an arithmetic number, because the mean of its divisors is an integer number (180846123).

Almost surely, 2^721109381 is an apocalyptic number.

It is an amenable number.

721109381 is a deficient number, since it is larger than the sum of its proper divisors (2275111).

721109381 is a wasteful number, since it uses less digits than its factorization.

721109381 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2275110.

The product of its (nonzero) digits is 3024, while the sum is 32.

The square root of 721109381 is about 26853.4798676075. The cubic root of 721109381 is about 896.7410450563.

The spelling of 721109381 in words is "seven hundred twenty-one million, one hundred nine thousand, three hundred eighty-one".