1661400543 has 24 divisors (see below), whose sum is σ = 2437343104. Its totient is φ = 1005895440.

The previous prime is 1661400539. The next prime is 1661400551. The reversal of 1661400543 is 3450041661.

It is not a de Polignac number, because 1661400543 - 2² = 1661400539 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 1661400543.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1661400553) by changing a digit.

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 23 ways as a sum of consecutive naturals, for example, 523680 + ... + 526842.

Almost surely, 2^1661400543 is an apocalyptic number.

1661400543 is a deficient number, since it is larger than the sum of its proper divisors (775942561).

1661400543 is a wasteful number, since it uses less digits than its factorization.

1661400543 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 4635 (or 4624 counting only the distinct ones).

The product of its (nonzero) digits is 8640, while the sum is 30.

The square root of 1661400543 is about 40760.2814391658. The cubic root of 1661400543 is about 1184.3810479828.

It can be divided in two parts, 1661 and 400543, that added together give a palindrome (402204).

The spelling of 1661400543 in words is "one billion, six hundred sixty-one million, four hundred thousand, five hundred forty-three".