23145721 has 9 divisors (see below), whose sum is σ = 24674511. Its totient is φ = 21707232.

The previous prime is 23145713. The next prime is 23145791. The reversal of 23145721 is 12754132.

It is a happy number.

The square root of 23145721 is 4811.

It is a perfect power (a square), and thus also a powerful number.

It can be written as a sum of positive squares in only one way, i.e., 18020025 + 5125696 = 4245^2 + 2264^2 .

It is not a de Polignac number, because 23145721 - 2³ = 23145713 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (23145791) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 8 ways as a sum of consecutive naturals, for example, 81646 + ... + 81928.

Almost surely, 2^23145721 is an apocalyptic number.

23145721 is the 4811-st square number.

23145721 is the 2406-th centered octagonal number.

It is an amenable number.

23145721 is a deficient number, since it is larger than the sum of its proper divisors (1528790).

23145721 is an frugal number, since it uses more digits than its factorization.

23145721 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 600 (or 300 counting only the distinct ones).

The product of its digits is 1680, while the sum is 25.

The cubic root of 23145721 is about 284.9860298887.

Multiplying 23145721 by its sum of digits (25), we get a square (578643025 = 24055²).

Adding to 23145721 its reverse (12754132), we get a palindrome (35899853).

The spelling of 23145721 in words is "twenty-three million, one hundred forty-five thousand, seven hundred twenty-one".