121557636 has 36 divisors (see below), whose sum is σ = 307907964. Its totient is φ = 40435200.

The previous prime is 121557607. The next prime is 121557637. The reversal of 121557636 is 636755121.

121557636 is a `hidden beast` number, since 1 + 2 + 15 + 5 + 7 + 636 = 666.

It can be written as a sum of positive squares in 2 ways, for example, as 81108036 + 40449600 = 9006^2 + 6360^2 .

It is a tau number, because it is divible by the number of its divisors (36).

It is a Harshad number since it is a multiple of its sum of digits (36).

It is a self number, because there is not a number n which added to its sum of digits gives 121557636.

It is not an unprimeable number, because it can be changed into a prime (121557637) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 15516 + ... + 21996.

It is an arithmetic number, because the mean of its divisors is an integer number (8552999).

Almost surely, 2^121557636 is an apocalyptic number.

It is an amenable number.

121557636 is an abundant number, since it is smaller than the sum of its proper divisors (186350328).

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

121557636 is a wasteful number, since it uses less digits than its factorization.

121557636 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 7012 (or 7007 counting only the distinct ones).

The product of its digits is 37800, while the sum is 36.

The square root of 121557636 is about 11025.3179545989. The cubic root of 121557636 is about 495.3673917763.

It can be divided in two parts, 12155 and 7636, that added together give a palindrome (19791).

The spelling of 121557636 in words is "one hundred twenty-one million, five hundred fifty-seven thousand, six hundred thirty-six".