1221165554958 has 48 divisors (see below), whose sum is σ = 2653614812160. Its totient is φ = 405862271568.

The previous prime is 1221165554927. The next prime is 1221165554981. The reversal of 1221165554958 is 8594555611221.

1221165554958 is a `hidden beast` number, since 1 + 2 + 21 + 1 + 65 + 554 + 9 + 5 + 8 = 666.

It is a Curzon number.

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 88438491 + ... + 88452297.

It is an arithmetic number, because the mean of its divisors is an integer number (55283641920).

Almost surely, 2^{1221165554958} is an apocalyptic number.

1221165554958 is a gapful number since it is divisible by the number (18) formed by its first and last digit.

1221165554958 is an abundant number, since it is smaller than the sum of its proper divisors (1432449257202).

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

1221165554958 is a wasteful number, since it uses less digits than its factorization.

1221165554958 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 27861 (or 27858 counting only the distinct ones).

The product of its digits is 4320000, while the sum is 54.

The spelling of 1221165554958 in words is "one trillion, two hundred twenty-one billion, one hundred sixty-five million, five hundred fifty-four thousand, nine hundred fifty-eight".