138128761 has 4 divisors (see below), whose sum is σ = 139419792. Its totient is φ = 136837732.

The previous prime is 138128737. The next prime is 138128779. The reversal of 138128761 is 167821831.

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 138128761 - 2⁷ = 138128633 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 138128761.

It is not an unprimeable number, because it can be changed into a prime (138123761) 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, 645355 + ... + 645568.

It is an arithmetic number, because the mean of its divisors is an integer number (34854948).

Almost surely, 2^138128761 is an apocalyptic number.

It is an amenable number.

138128761 is a deficient number, since it is larger than the sum of its proper divisors (1291031).

138128761 is a wasteful number, since it uses less digits than its factorization.

138128761 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1291030.

The product of its digits is 16128, while the sum is 37.

The square root of 138128761 is about 11752.8192787943. The cubic root of 138128761 is about 516.9255979041.

The spelling of 138128761 in words is "one hundred thirty-eight million, one hundred twenty-eight thousand, seven hundred sixty-one".