1221404401661 has 8 divisors (see below), whose sum is σ = 1251350262624. Its totient is φ = 1191528591120.

The previous prime is 1221404401649. The next prime is 1221404401703. The reversal of 1221404401661 is 1661044041221.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-1221404401661 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1221404461661) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 17477306 + ... + 17547051.

It is an arithmetic number, because the mean of its divisors is an integer number (156418782828).

Almost surely, 2^{1221404401661} is an apocalyptic number.

It is an amenable number.

1221404401661 is a deficient number, since it is larger than the sum of its proper divisors (29945860963).

1221404401661 is an equidigital number, since it uses as much as digits as its factorization.

1221404401661 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 35025211.

The product of its (nonzero) digits is 9216, while the sum is 32.

Adding to 1221404401661 its reverse (1661044041221), we get a palindrome (2882448442882).

The spelling of 1221404401661 in words is "one trillion, two hundred twenty-one billion, four hundred four million, four hundred one thousand, six hundred sixty-one".