126172021 has 4 divisors (see below), whose sum is σ = 126360172. Its totient is φ = 125983872.

The previous prime is 126172009. The next prime is 126172037. The reversal of 126172021 is 120271621.

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: 120271621 = 6841 ⋅17581.

It can be written as a sum of positive squares in 2 ways, for example, as 45711121 + 80460900 = 6761^2 + 8970^2 .

It is a cyclic number.

It is not a de Polignac number, because 126172021 - 2⁷ = 126171893 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 126171983 and 126172001.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (126172051) 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, 93066 + ... + 94411.

It is an arithmetic number, because the mean of its divisors is an integer number (31590043).

Almost surely, 2^126172021 is an apocalyptic number.

It is an amenable number.

126172021 is a deficient number, since it is larger than the sum of its proper divisors (188151).

126172021 is an equidigital number, since it uses as much as digits as its factorization.

126172021 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 188150.

The product of its (nonzero) digits is 336, while the sum is 22.

The square root of 126172021 is about 11232.6319711811. The cubic root of 126172021 is about 501.5578359203.

The spelling of 126172021 in words is "one hundred twenty-six million, one hundred seventy-two thousand, twenty-one".