655540121 has 2 divisors, whose sum is σ = 655540122. Its totient is φ = 655540120.

The previous prime is 655540097. The next prime is 655540139. The reversal of 655540121 is 121045556.

It is a happy number.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 443692096 + 211848025 = 21064^2 + 14555^2 .

It is a cyclic number.

It is not a de Polignac number, because 655540121 - 2¹⁰ = 655539097 is a prime.

It is a super-3 number, since 3×655540121³ (a number of 27 digits) contains 333 as substring.

It is not a weakly prime, because it can be changed into another prime (655540421) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 327770060 + 327770061.

It is an arithmetic number, because the mean of its divisors is an integer number (327770061).

Almost surely, 2^655540121 is an apocalyptic number.

It is an amenable number.

655540121 is a deficient number, since it is larger than the sum of its proper divisors (1).

655540121 is an equidigital number, since it uses as much as digits as its factorization.

655540121 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 6000, while the sum is 29.

The square root of 655540121 is about 25603.5177465910. The cubic root of 655540121 is about 868.6932074324.

Adding to 655540121 its reverse (121045556), we get a palindrome (776585677).

The spelling of 655540121 in words is "six hundred fifty-five million, five hundred forty thousand, one hundred twenty-one".