1218115421 has 4 divisors (see below), whose sum is σ = 1227414144. Its totient is φ = 1208816700.

The previous prime is 1218115411. The next prime is 1218115469. The reversal of 1218115421 is 1245118121.

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: 1245118121 = 13 ⋅95778317.

It is a cyclic number.

It is not a de Polignac number, because 1218115421 - 2¹⁸ = 1217853277 is a prime.

It is a Duffinian number.

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1218115411) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 4649165 + ... + 4649426.

It is an arithmetic number, because the mean of its divisors is an integer number (306853536).

Almost surely, 2^1218115421 is an apocalyptic number.

It is an amenable number.

1218115421 is a deficient number, since it is larger than the sum of its proper divisors (9298723).

1218115421 is an equidigital number, since it uses as much as digits as its factorization.

1218115421 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 9298722.

The product of its digits is 640, while the sum is 26.

The square root of 1218115421 is about 34901.5102968339. The cubic root of 1218115421 is about 1067.9792475055.

The spelling of 1218115421 in words is "one billion, two hundred eighteen million, one hundred fifteen thousand, four hundred twenty-one".