1661406400 has 84 divisors (see below), whose sum is σ = 4111645320. Its totient is φ = 660736000.

The previous prime is 1661406391. The next prime is 1661406401. The reversal of 1661406400 is 46041661.

It is a zygodrome in base 2.

It is not an unprimeable number, because it can be changed into a prime (1661406401) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 283500 + ... + 289300.

Almost surely, 2^1661406400 is an apocalyptic number.

1661406400 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 1661406400, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (2055822660).

1661406400 is an abundant number, since it is smaller than the sum of its proper divisors (2450238920).

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

1661406400 is a wasteful number, since it uses less digits than its factorization.

1661406400 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 6002 (or 5987 counting only the distinct ones).

The product of its (nonzero) digits is 3456, while the sum is 28.

The square root of 1661406400 is about 40760.3532860058. The cubic root of 1661406400 is about 1184.3824397627.

The spelling of 1661406400 in words is "one billion, six hundred sixty-one million, four hundred six thousand, four hundred".