138415021 has 4 divisors (see below), whose sum is σ = 138447232. Its totient is φ = 138382812.

The previous prime is 138415009. The next prime is 138415049. The reversal of 138415021 is 120514831.

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 not a de Polignac number, because 138415021 - 2¹⁵ = 138382253 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 (138415091) 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, 8445 + ... + 18658.

It is an arithmetic number, because the mean of its divisors is an integer number (34611808).

Almost surely, 2^138415021 is an apocalyptic number.

It is an amenable number.

138415021 is a deficient number, since it is larger than the sum of its proper divisors (32211).

138415021 is an equidigital number, since it uses as much as digits as its factorization.

138415021 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 32210.

The product of its (nonzero) digits is 960, while the sum is 25.

The square root of 138415021 is about 11764.9913302136. The cubic root of 138415021 is about 517.2824461478.

Adding to 138415021 its reverse (120514831), we get a palindrome (258929852).

The spelling of 138415021 in words is "one hundred thirty-eight million, four hundred fifteen thousand, twenty-one".