42121813 has 4 divisors (see below), whose sum is σ = 42134860. Its totient is φ = 42108768.

The previous prime is 42121787. The next prime is 42121819. The reversal of 42121813 is 31812124.

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 22212369 + 19909444 = 4713^2 + 4462^2 .

It is a cyclic number.

It is not a de Polignac number, because 42121813 - 2⁹ = 42121301 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (42121819) 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, 2281 + ... + 9457.

It is an arithmetic number, because the mean of its divisors is an integer number (10533715).

Almost surely, 2^42121813 is an apocalyptic number.

It is an amenable number.

42121813 is a deficient number, since it is larger than the sum of its proper divisors (13047).

42121813 is an equidigital number, since it uses as much as digits as its factorization.

42121813 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 13046.

The product of its digits is 384, while the sum is 22.

The square root of 42121813 is about 6490.1319709232. The cubic root of 42121813 is about 347.9383918992.

Adding to 42121813 its reverse (31812124), we get a palindrome (73933937).

The spelling of 42121813 in words is "forty-two million, one hundred twenty-one thousand, eight hundred thirteen".