18661515400 has 144 divisors (see below), whose sum is σ = 50497432020. Its totient is φ = 6386688000.

The previous prime is 18661515371. The next prime is 18661515401. The reversal of 18661515400 is 451516681.

It can be written as a sum of positive squares in 6 ways, for example, as 3314765476 + 15346749924 = 57574^2 + 123882^2 .

It is a self number, because there is not a number n which added to its sum of digits gives 18661515400.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (18661515401) by changing a digit.

It is a polite number, since it can be written in 35 ways as a sum of consecutive naturals, for example, 388720 + ... + 434080.

Almost surely, 2^18661515400 is an apocalyptic number.

18661515400 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 18661515400, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (25248716010).

18661515400 is an abundant number, since it is smaller than the sum of its proper divisors (31835916620).

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

18661515400 is a wasteful number, since it uses less digits than its factorization.

18661515400 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 45416 (or 45396 counting only the distinct ones).

The product of its (nonzero) digits is 28800, while the sum is 37.

It can be divided in two parts, 18661 and 515400, that added together give a triangular number (534061 = T₁₀₃₃).

The spelling of 18661515400 in words is "eighteen billion, six hundred sixty-one million, five hundred fifteen thousand, four hundred".