68640138 has 48 divisors (see below), whose sum is σ = 175458816. Its totient is φ = 18977760.

The previous prime is 68640133. The next prime is 68640149. The reversal of 68640138 is 83104686.

It is a happy number.

68640138 is a `hidden beast` number, since 6 + 8 + 640 + 1 + 3 + 8 = 666.

It is a super-2 number, since 2×68640138² = 9422937089318088, which contains 22 as substring.

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (68640133) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 4881 + ... + 12692.

It is an arithmetic number, because the mean of its divisors is an integer number (3655392).

Almost surely, 2^68640138 is an apocalyptic number.

68640138 is an abundant number, since it is smaller than the sum of its proper divisors (106818678).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

68640138 is a wasteful number, since it uses less digits than its factorization.

68640138 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 17619 (or 17616 counting only the distinct ones).

The product of its (nonzero) digits is 27648, while the sum is 36.

The square root of 68640138 is about 8284.9343992575. The cubic root of 68640138 is about 409.4423073916.

The spelling of 68640138 in words is "sixty-eight million, six hundred forty thousand, one hundred thirty-eight".