1221801817878 has 24 divisors (see below), whose sum is σ = 2690634606816. Its totient is φ = 400590759600.

The previous prime is 1221801817853. The next prime is 1221801817883. The reversal of 1221801817878 is 8787181081221.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 556374958 + ... + 556377153.

It is an arithmetic number, because the mean of its divisors is an integer number (112109775284).

Almost surely, 2^{1221801817878} is an apocalyptic number.

1221801817878 is a gapful number since it is divisible by the number (18) formed by its first and last digit.

1221801817878 is an abundant number, since it is smaller than the sum of its proper divisors (1468832788938).

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

1221801817878 is a wasteful number, since it uses less digits than its factorization.

1221801817878 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1112752180 (or 1112752177 counting only the distinct ones).

The product of its (nonzero) digits is 802816, while the sum is 54.

The spelling of 1221801817878 in words is "one trillion, two hundred twenty-one billion, eight hundred one million, eight hundred seventeen thousand, eight hundred seventy-eight".