12145721 has 4 divisors (see below), whose sum is σ = 13880832. Its totient is φ = 10410612.

The previous prime is 12145711. The next prime is 12145723. The reversal of 12145721 is 12754121.

12145721 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, and also a Blum integer, because the two primes are equal to 3 mod 4, and also an emirpimes, since its reverse is a distinct semiprime: 12754121 = 23 ⋅554527.

It is a cyclic number.

It is not a de Polignac number, because 12145721 - 2¹⁰ = 12144697 is a prime.

It is not an unprimeable number, because it can be changed into a prime (12145723) 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, 867545 + ... + 867558.

It is an arithmetic number, because the mean of its divisors is an integer number (3470208).

Almost surely, 2^12145721 is an apocalyptic number.

It is an amenable number.

12145721 is a deficient number, since it is larger than the sum of its proper divisors (1735111).

12145721 is an equidigital number, since it uses as much as digits as its factorization.

12145721 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1735110.

The product of its digits is 560, while the sum is 23.

The square root of 12145721 is about 3485.0711613969. The cubic root of 12145721 is about 229.8658385816.

Adding to 12145721 its reverse (12754121), we get a palindrome (24899842).

Subtracting 12145721 from its reverse (12754121), we obtain a square (608400 = 780²).

The spelling of 12145721 in words is "twelve million, one hundred forty-five thousand, seven hundred twenty-one".