23151721 has 4 divisors (see below), whose sum is σ = 23163012. Its totient is φ = 23140432.

The previous prime is 23151707. The next prime is 23151727. The reversal of 23151721 is 12715132.

It is a happy number.

It is a semiprime because it is the product of two primes, and also a brilliant number, because the two primes have the same length.

It can be written as a sum of positive squares in 2 ways, for example, as 13039321 + 10112400 = 3611^2 + 3180^2 .

It is a cyclic number.

It is not a de Polignac number, because 23151721 - 2¹¹ = 23149673 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 23151692 and 23151701.

It is not an unprimeable number, because it can be changed into a prime (23151727) 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, 1606 + ... + 6991.

It is an arithmetic number, because the mean of its divisors is an integer number (5790753).

Almost surely, 2^23151721 is an apocalyptic number.

It is an amenable number.

23151721 is a deficient number, since it is larger than the sum of its proper divisors (11291).

23151721 is an equidigital number, since it uses as much as digits as its factorization.

23151721 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 11290.

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

The square root of 23151721 is about 4811.6235305768. The cubic root of 23151721 is about 285.0106531362.

Adding to 23151721 its reverse (12715132), we get a palindrome (35866853).

The spelling of 23151721 in words is "twenty-three million, one hundred fifty-one thousand, seven hundred twenty-one".