1221326817816 has 64 divisors (see below), whose sum is σ = 3641222822400. Its totient is φ = 333778756608.

The previous prime is 1221326817719. The next prime is 1221326817817. The reversal of 1221326817816 is 6187186231221.

It is a nude number because it is divisible by every one of its digits.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1221326817817) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 158035321 + ... + 158043048.

It is an arithmetic number, because the mean of its divisors is an integer number (56894106600).

Almost surely, 2^{1221326817816} is an apocalyptic number.

It is an amenable number.

1221326817816 is an abundant number, since it is smaller than the sum of its proper divisors (2419896004584).

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

1221326817816 is a wasteful number, since it uses less digits than its factorization.

1221326817816 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 316078408 (or 316078404 counting only the distinct ones).

The product of its digits is 387072, while the sum is 48.

The spelling of 1221326817816 in words is "one trillion, two hundred twenty-one billion, three hundred twenty-six million, eight hundred seventeen thousand, eight hundred sixteen".