121555220 has 24 divisors (see below), whose sum is σ = 258765864. Its totient is φ = 47955456.

The previous prime is 121555183. The next prime is 121555229. The reversal of 121555220 is 22555121.

It can be written as a sum of positive squares in 4 ways, for example, as 35473936 + 86081284 = 5956^2 + 9278^2 .

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (121555229) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 40169 + ... + 43088.

It is an arithmetic number, because the mean of its divisors is an integer number (10781911).

Almost surely, 2^121555220 is an apocalyptic number.

121555220 is a gapful number since it is divisible by the number (10) formed by its first and last digit.

It is an amenable number.

121555220 is an abundant number, since it is smaller than the sum of its proper divisors (137210644).

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

121555220 is a wasteful number, since it uses less digits than its factorization.

121555220 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 83339 (or 83337 counting only the distinct ones).

The product of its (nonzero) digits is 1000, while the sum is 23.

The square root of 121555220 is about 11025.2083880533. The cubic root of 121555220 is about 495.3641098886.

Subtracting from 121555220 its reverse (22555121), we obtain a palindrome (99000099).

The spelling of 121555220 in words is "one hundred twenty-one million, five hundred fifty-five thousand, two hundred twenty".