1665716451840 has 400 divisors, whose sum is σ = 6818371667712. Its totient is φ = 380734857216.

The previous prime is 1665716451809. The next prime is 1665716451877. The reversal of 1665716451840 is 481546175661.

1665716451840 is a `hidden beast` number, since 1 + 6 + 6 + 571 + 64 + 5 + 1 + 8 + 4 + 0 = 666.

It is a super-2 number, since 2×1665716451840² (a number of 25 digits) contains 22 as substring.

It is a Harshad number since it is a multiple of its sum of digits (54).

It is an unprimeable number.

It is a polite number, since it can be written in 39 ways as a sum of consecutive naturals, for example, 877737 + ... + 2025303.

Almost surely, 2^{1665716451840} is an apocalyptic number.

1665716451840 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 1665716451840, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (3409185833856).

1665716451840 is an abundant number, since it is smaller than the sum of its proper divisors (5152655215872).

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

1665716451840 is an equidigital number, since it uses as much as digits as its factorization.

1665716451840 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1147609 (or 1147584 counting only the distinct ones).

The product of its (nonzero) digits is 4838400, while the sum is 54.

The spelling of 1665716451840 in words is "one trillion, six hundred sixty-five billion, seven hundred sixteen million, four hundred fifty-one thousand, eight hundred forty".