1661321651400 has 144 divisors (see below), whose sum is σ = 5584536802260. Its totient is φ = 442601049600.

The previous prime is 1661321651399. The next prime is 1661321651441. The reversal of 1661321651400 is 41561231661.

1661321651400 is a `hidden beast` number, since 1 + 6 + 6 + 132 + 1 + 6 + 514 + 0 + 0 = 666.

It can be written as a sum of positive squares in 6 ways, for example, as 179828579844 + 1481493071556 = 424062^2 + 1217166^2 .

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

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 35 ways as a sum of consecutive naturals, for example, 1474854 + ... + 2344746.

Almost surely, 2^{1661321651400} is an apocalyptic number.

1661321651400 is a gapful number since it is divisible by the number (10) formed by its first and last digit.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 1661321651400, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (2792268401130).

1661321651400 is an abundant number, since it is smaller than the sum of its proper divisors (3923215150860).

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

1661321651400 is a wasteful number, since it uses less digits than its factorization.

1661321651400 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 870976 (or 870964 counting only the distinct ones).

The product of its (nonzero) digits is 25920, while the sum is 36.

The spelling of 1661321651400 in words is "one trillion, six hundred sixty-one billion, three hundred twenty-one million, six hundred fifty-one thousand, four hundred".