121638406 has 4 divisors (see below), whose sum is σ = 182457612. Its totient is φ = 60819202.

The previous prime is 121638401. The next prime is 121638449. The reversal of 121638406 is 604836121.

It is a happy number.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 604836121 = 139 ⋅4351339.

It is a Smith number, since the sum of its digits (31) coincides with the sum of the digits of its prime factors. Since it is squarefree, it is also a hoax number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (121638401) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 30409600 + ... + 30409603.

It is an arithmetic number, because the mean of its divisors is an integer number (45614403).

Almost surely, 2^121638406 is an apocalyptic number.

121638406 is a deficient number, since it is larger than the sum of its proper divisors (60819206).

121638406 is an equidigital number, since it uses as much as digits as its factorization.

121638406 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 60819205.

The product of its (nonzero) digits is 6912, while the sum is 31.

The square root of 121638406 is about 11028.9802792461. The cubic root of 121638406 is about 495.4770845031.

The spelling of 121638406 in words is "one hundred twenty-one million, six hundred thirty-eight thousand, four hundred six".