1644505551556 has 96 divisors (see below), whose sum is σ = 3525691986432. Its totient is φ = 655753190400.

The previous prime is 1644505551539. The next prime is 1644505551643. The reversal of 1644505551556 is 6551555054461.

It is a super-2 number, since 2×1644505551556² (a number of 25 digits) contains 22 as substring.

It is an unprimeable number.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 130499656 + ... + 130512256.

It is an arithmetic number, because the mean of its divisors is an integer number (36725958192).

Almost surely, 2^{1644505551556} is an apocalyptic number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 1644505551556, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (1762845993216).

1644505551556 is an abundant number, since it is smaller than the sum of its proper divisors (1881186434876).

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

1644505551556 is a wasteful number, since it uses less digits than its factorization.

1644505551556 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 18149 (or 18147 counting only the distinct ones).

The product of its (nonzero) digits is 9000000, while the sum is 52.

The spelling of 1644505551556 in words is "one trillion, six hundred forty-four billion, five hundred five million, five hundred fifty-one thousand, five hundred fifty-six".