131221639 has 4 divisors (see below), whose sum is σ = 131785056. Its totient is φ = 130658224.

The previous prime is 131221637. The next prime is 131221669. The reversal of 131221639 is 936122131.

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

It is a cyclic number.

It is not a de Polignac number, because 131221639 - 2¹ = 131221637 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 (131221633) 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 3 ways as a sum of consecutive naturals, for example, 281359 + ... + 281824.

It is an arithmetic number, because the mean of its divisors is an integer number (32946264).

Almost surely, 2^131221639 is an apocalyptic number.

131221639 is a deficient number, since it is larger than the sum of its proper divisors (563417).

131221639 is an equidigital number, since it uses as much as digits as its factorization.

131221639 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 563416.

The product of its digits is 1944, while the sum is 28.

The square root of 131221639 is about 11455.2013949996. The cubic root of 131221639 is about 508.1615713044.

The spelling of 131221639 in words is "one hundred thirty-one million, two hundred twenty-one thousand, six hundred thirty-nine".