2181397680 has 720 divisors, whose sum is σ = 9519182400. Its totient is φ = 447068160.

The previous prime is 2181397663. The next prime is 2181397709. The reversal of 2181397680 is 867931812.

2181397680 is a `hidden beast` number, since 2 + 181 + 397 + 6 + 80 = 666.

It is a tau number, because it is divible by the number of its divisors (720).

It is a Harshad number since it is a multiple of its sum of digits (45).

It is an unprimeable number.

It is a polite number, since it can be written in 143 ways as a sum of consecutive naturals, for example, 29882124 + ... + 29882196.

Almost surely, 2^2181397680 is an apocalyptic number.

2181397680 is a gapful number since it is divisible by the number (20) 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 2181397680, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (4759591200).

2181397680 is an abundant number, since it is smaller than the sum of its proper divisors (7337784720).

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

2181397680 is a wasteful number, since it uses less digits than its factorization.

2181397680 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 135 (or 101 counting only the distinct ones).

The product of its (nonzero) digits is 145152, while the sum is 45.

The square root of 2181397680 is about 46705.4352297460. The cubic root of 2181397680 is about 1296.9153056269.

The spelling of 2181397680 in words is "two billion, one hundred eighty-one million, three hundred ninety-seven thousand, six hundred eighty".