121638 has 32 divisors (see below), whose sum is σ = 282240. Its totient is φ = 34560.

The previous prime is 121637. The next prime is 121661. The reversal of 121638 is 836121.

It is an Ulam number.

It is an alternating number because its digits alternate between odd and even.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (121631) 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, 1206 + ... + 1302.

It is an arithmetic number, because the mean of its divisors is an integer number (8820).

2¹²¹⁶³⁸ is an apocalyptic number.

It is a practical number, because each smaller number is the sum of distinct divisors of 121638, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (141120).

121638 is an abundant number, since it is smaller than the sum of its proper divisors (160602).

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

121638 is a wasteful number, since it uses less digits than its factorization.

121638 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 132.

The product of its digits is 288, while the sum is 21.

The square root of 121638 is about 348.7663974640. The cubic root of 121638 is about 49.5476533241.

Adding to 121638 its reverse (836121), we get a palindrome (957759).

The spelling of 121638 in words is "one hundred twenty-one thousand, six hundred thirty-eight".