137991421 has 4 divisors (see below), whose sum is σ = 143991072. Its totient is φ = 131991772.

The previous prime is 137991379. The next prime is 137991437. The reversal of 137991421 is 124199731.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-137991421 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 (137991481) 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, 2999791 + ... + 2999836.

It is an arithmetic number, because the mean of its divisors is an integer number (35997768).

Almost surely, 2^137991421 is an apocalyptic number.

It is an amenable number.

137991421 is a deficient number, since it is larger than the sum of its proper divisors (5999651).

137991421 is an equidigital number, since it uses as much as digits as its factorization.

137991421 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 5999650.

The product of its digits is 13608, while the sum is 37.

The square root of 137991421 is about 11746.9749723067. The cubic root of 137991421 is about 516.7542164968.

The spelling of 137991421 in words is "one hundred thirty-seven million, nine hundred ninety-one thousand, four hundred twenty-one".