138509581 has 16 divisors (see below), whose sum is σ = 164118528. Its totient is φ = 114390000.

The previous prime is 138509573. The next prime is 138509621. The reversal of 138509581 is 185905831.

It is not a de Polignac number, because 138509581 - 2³ = 138509573 is a prime.

It is a super-2 number, since 2×138509581² = 38369808057591122, which contains 22 as substring.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (138509551) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 53196 + ... + 55738.

It is an arithmetic number, because the mean of its divisors is an integer number (10257408).

Almost surely, 2^138509581 is an apocalyptic number.

It is an amenable number.

138509581 is a deficient number, since it is larger than the sum of its proper divisors (25608947).

138509581 is a wasteful number, since it uses less digits than its factorization.

138509581 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2832.

The product of its (nonzero) digits is 43200, while the sum is 40.

The square root of 138509581 is about 11769.0093465848. The cubic root of 138509581 is about 517.4002153831.

The spelling of 138509581 in words is "one hundred thirty-eight million, five hundred nine thousand, five hundred eighty-one".