138816561 has 8 divisors (see below), whose sum is σ = 199326400. Its totient is φ = 85425552.

The previous prime is 138816553. The next prime is 138816583. The reversal of 138816561 is 165618831.

It is a sphenic number, since it is the product of 3 distinct primes.

It is not a de Polignac number, because 138816561 - 2³ = 138816553 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (39), and also a Moran number because the ratio is a prime number: 3559399 = 138816561 / (1 + 3 + 8 + 8 + 1 + 6 + 5 + 6 + 1).

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (138816511) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 1779661 + ... + 1779738.

It is an arithmetic number, because the mean of its divisors is an integer number (24915800).

Almost surely, 2^138816561 is an apocalyptic number.

It is an amenable number.

138816561 is a deficient number, since it is larger than the sum of its proper divisors (60509839).

138816561 is a wasteful number, since it uses less digits than its factorization.

138816561 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3559415.

The product of its digits is 34560, while the sum is 39.

The square root of 138816561 is about 11782.0440077263. The cubic root of 138816561 is about 517.7821728894.

The spelling of 138816561 in words is "one hundred thirty-eight million, eight hundred sixteen thousand, five hundred sixty-one".