121557 has 4 divisors (see below), whose sum is σ = 162080. Its totient is φ = 81036.

The previous prime is 121553. The next prime is 121559. The reversal of 121557 is 755121.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4, and also an emirpimes, since its reverse is a distinct semiprime: 755121 = 3 ⋅251707.

It is not a de Polignac number, because 121557 - 2² = 121553 is a prime.

It is a super-2 number, since 2×121557² = 29552208498, which contains 22 as substring.

It is a D-number.

It is a Duffinian number.

121557 is a lucky number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (121553) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 20257 + ... + 20262.

It is an arithmetic number, because the mean of its divisors is an integer number (40520).

2¹²¹⁵⁵⁷ is an apocalyptic number.

It is an amenable number.

121557 is a deficient number, since it is larger than the sum of its proper divisors (40523).

121557 is an equidigital number, since it uses as much as digits as its factorization.

121557 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 40522.

The product of its digits is 350, while the sum is 21.

The square root of 121557 is about 348.6502545532. The cubic root of 121557 is about 49.5366527840.

Adding to 121557 its reverse (755121), we get a palindrome (876678).

The spelling of 121557 in words is "one hundred twenty-one thousand, five hundred fifty-seven".