42131921 has 4 divisors (see below), whose sum is σ = 45372852. Its totient is φ = 38890992.

The previous prime is 42131909. The next prime is 42131923. The reversal of 42131921 is 12913124.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 21520321 + 20611600 = 4639^2 + 4540^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-42131921 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (42131923) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 1620446 + ... + 1620471.

It is an arithmetic number, because the mean of its divisors is an integer number (11343213).

Almost surely, 2^42131921 is an apocalyptic number.

It is an amenable number.

42131921 is a deficient number, since it is larger than the sum of its proper divisors (3240931).

42131921 is a wasteful number, since it uses less digits than its factorization.

42131921 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3240930.

The product of its digits is 432, while the sum is 23.

The square root of 42131921 is about 6490.9106448941. The cubic root of 42131921 is about 347.9662213437.

The spelling of 42131921 in words is "forty-two million, one hundred thirty-one thousand, nine hundred twenty-one".