126640021 has 8 divisors (see below), whose sum is σ = 137360664. Its totient is φ = 116282880.

The previous prime is 126640009. The next prime is 126640027. The reversal of 126640021 is 120046621.

It can be written as a sum of positive squares in 4 ways, for example, as 3651921 + 122988100 = 1911^2 + 11090^2 .

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 126640021 - 2⁷ = 126639893 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 126639974 and 126640001.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (126640027) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 90150 + ... + 91543.

It is an arithmetic number, because the mean of its divisors is an integer number (17170083).

Almost surely, 2^126640021 is an apocalyptic number.

It is an amenable number.

126640021 is a deficient number, since it is larger than the sum of its proper divisors (10720643).

126640021 is a wasteful number, since it uses less digits than its factorization.

126640021 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 181751.

The product of its (nonzero) digits is 576, while the sum is 22.

The square root of 126640021 is about 11253.4448503558. Note that the first 3 decimals coincide. The cubic root of 126640021 is about 502.1772005021.

Adding to 126640021 its reverse (120046621), we get a palindrome (246686642).

The spelling of 126640021 in words is "one hundred twenty-six million, six hundred forty thousand, twenty-one".