105721321 has 4 divisors (see below), whose sum is σ = 108578692. Its totient is φ = 102863952.

The previous prime is 105721307. The next prime is 105721349. The reversal of 105721321 is 123127501.

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: 123127501 = 7 ⋅17589643.

It can be written as a sum of positive squares in 2 ways, for example, as 48930025 + 56791296 = 6995^2 + 7536^2 .

It is a cyclic number.

It is not a de Polignac number, because 105721321 - 2⁵ = 105721289 is a prime.

It is a super-2 number, since 2×105721321² = 22353995427970082, which contains 22 as substring.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 105721292 and 105721301.

It is not an unprimeable number, because it can be changed into a prime (105721361) 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, 1428630 + ... + 1428703.

It is an arithmetic number, because the mean of its divisors is an integer number (27144673).

Almost surely, 2^105721321 is an apocalyptic number.

It is an amenable number.

105721321 is a deficient number, since it is larger than the sum of its proper divisors (2857371).

105721321 is an equidigital number, since it uses as much as digits as its factorization.

105721321 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2857370.

The product of its (nonzero) digits is 420, while the sum is 22.

The square root of 105721321 is about 10282.0873853513. The cubic root of 105721321 is about 472.8472421117.

Adding to 105721321 its reverse (123127501), we get a palindrome (228848822).

It can be divided in two parts, 105721 and 321, that multiplied together give a triangular number (33936441 = T₈₂₃₈).

The spelling of 105721321 in words is "one hundred five million, seven hundred twenty-one thousand, three hundred twenty-one".