137821 has 4 divisors (see below), whose sum is σ = 138592. Its totient is φ = 137052.

The previous prime is 137803. The next prime is 137827. The reversal of 137821 is 128731.

137821 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

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, and also a brilliant number, because the two primes have the same length.

It is a cyclic number.

It is not a de Polignac number, because 137821 - 2¹³ = 129629 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 137792 and 137801.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (137827) 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, 40 + ... + 526.

It is an arithmetic number, because the mean of its divisors is an integer number (34648).

2¹³⁷⁸²¹ is an apocalyptic number.

It is an amenable number.

137821 is a deficient number, since it is larger than the sum of its proper divisors (771).

137821 is an equidigital number, since it uses as much as digits as its factorization.

137821 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 770.

The product of its digits is 336, while the sum is 22.

The square root of 137821 is about 371.2425083419. The cubic root of 137821 is about 51.6541396384.

The spelling of 137821 in words is "one hundred thirty-seven thousand, eight hundred twenty-one".