139940021 has 8 divisors (see below), whose sum is σ = 150806040. Its totient is φ = 129088512.

The previous prime is 139939999. The next prime is 139940029. The reversal of 139940021 is 120049931.

It is a happy number.

It can be written as a sum of positive squares in 4 ways, for example, as 29920900 + 110019121 = 5470^2 + 10489^2 .

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

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-139940021 is a prime.

It is a Duffinian number.

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (139940029) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 24581 + ... + 29733.

It is an arithmetic number, because the mean of its divisors is an integer number (18850755).

Almost surely, 2^139940021 is an apocalyptic number.

It is an amenable number.

139940021 is a deficient number, since it is larger than the sum of its proper divisors (10866019).

139940021 is a wasteful number, since it uses less digits than its factorization.

139940021 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 7255.

The product of its (nonzero) digits is 1944, while the sum is 29.

The square root of 139940021 is about 11829.6247193222. The cubic root of 139940021 is about 519.1752470684.

Adding to 139940021 its reverse (120049931), we get a palindrome (259989952).

The spelling of 139940021 in words is "one hundred thirty-nine million, nine hundred forty thousand, twenty-one".