1645181972661 has 8 divisors (see below), whose sum is σ = 2198461435200. Its totient is φ = 1094345245952.

The previous prime is 1645181972627. The next prime is 1645181972671. The reversal of 1645181972661 is 1662791815461.

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

It is a cyclic number.

It is not a de Polignac number, because 1645181972661 - 2¹¹ = 1645181970613 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1645181972611) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (23) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 610682385 + ... + 610685078.

It is an arithmetic number, because the mean of its divisors is an integer number (274807679400).

Almost surely, 2^{1645181972661} is an apocalyptic number.

It is an amenable number.

1645181972661 is a deficient number, since it is larger than the sum of its proper divisors (553279462539).

1645181972661 is a wasteful number, since it uses less digits than its factorization.

1645181972661 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1221367915.

The product of its digits is 4354560, while the sum is 57.

The spelling of 1645181972661 in words is "one trillion, six hundred forty-five billion, one hundred eighty-one million, nine hundred seventy-two thousand, six hundred sixty-one".