138521566 has 4 divisors (see below), whose sum is σ = 207782352. Its totient is φ = 69260782.

The previous prime is 138521563. The next prime is 138521573. The reversal of 138521566 is 665125831.

138521566 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 an emirpimes, since its reverse is a distinct semiprime: 665125831 = 7351 ⋅90481.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (138521563) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 34630390 + ... + 34630393.

It is an arithmetic number, because the mean of its divisors is an integer number (51945588).

Almost surely, 2^138521566 is an apocalyptic number.

138521566 is a deficient number, since it is larger than the sum of its proper divisors (69260786).

138521566 is an equidigital number, since it uses as much as digits as its factorization.

138521566 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 69260785.

The product of its digits is 43200, while the sum is 37.

The square root of 138521566 is about 11769.5185118169. The cubic root of 138521566 is about 517.4151382081.

The spelling of 138521566 in words is "one hundred thirty-eight million, five hundred twenty-one thousand, five hundred sixty-six".