1221404401656 has 48 divisors (see below), whose sum is σ = 3338885885400. Its totient is φ = 403329799872.

The previous prime is 1221404401649. The next prime is 1221404401703. The reversal of 1221404401656 is 6561044041221.

1221404401656 is a `hidden beast` number, since 1 + 22 + 140 + 440 + 1 + 6 + 56 = 666.

It is a Harshad number since it is a multiple of its sum of digits (36).

It is a self number, because there is not a number n which added to its sum of digits gives 1221404401656.

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 11 ways as a sum of consecutive naturals, for example, 79263091 + ... + 79278498.

Almost surely, 2^{1221404401656} is an apocalyptic number.

It is an amenable number.

1221404401656 is an abundant number, since it is smaller than the sum of its proper divisors (2117481483744).

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

1221404401656 is a wasteful number, since it uses less digits than its factorization.

1221404401656 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 158541708 (or 158541701 counting only the distinct ones).

The product of its (nonzero) digits is 46080, while the sum is 36.

Adding to 1221404401656 its reverse (6561044041221), we get a palindrome (7782448442877).

The spelling of 1221404401656 in words is "one trillion, two hundred twenty-one billion, four hundred four million, four hundred one thousand, six hundred fifty-six".