138342821 has 4 divisors (see below), whose sum is σ = 146480652. Its totient is φ = 130204992.

The previous prime is 138342817. The next prime is 138342829. The reversal of 138342821 is 128243831.

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 71740900 + 66601921 = 8470^2 + 8161^2 .

It is a cyclic number.

It is not a de Polignac number, because 138342821 - 2² = 138342817 is a prime.

It is a super-2 number, since 2×138342821² = 38277472244476082, which contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (138342829) 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, 4068890 + ... + 4068923.

It is an arithmetic number, because the mean of its divisors is an integer number (36620163).

Almost surely, 2^138342821 is an apocalyptic number.

It is an amenable number.

138342821 is a deficient number, since it is larger than the sum of its proper divisors (8137831).

138342821 is an equidigital number, since it uses as much as digits as its factorization.

138342821 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 8137830.

The product of its digits is 9216, while the sum is 32.

The square root of 138342821 is about 11761.9225044208. The cubic root of 138342821 is about 517.1924889355.

The spelling of 138342821 in words is "one hundred thirty-eight million, three hundred forty-two thousand, eight hundred twenty-one".