2121780780 has 144 divisors (see below), whose sum is σ = 7401348864. Its totient is φ = 481956480.

The previous prime is 2121780757. The next prime is 2121780781. The reversal of 2121780780 is 870871212.

It is a happy number.

It is a Harshad number since it is a multiple of its sum of digits (36).

It is not an unprimeable number, because it can be changed into a prime (2121780781) by changing a digit.

It is a polite number, since it can be written in 47 ways as a sum of consecutive naturals, for example, 200215 + ... + 210545.

It is an arithmetic number, because the mean of its divisors is an integer number (51398256).

Almost surely, 2^2121780780 is an apocalyptic number.

2121780780 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 2121780780, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (3700674432).

2121780780 is an abundant number, since it is smaller than the sum of its proper divisors (5279568084).

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

2121780780 is a wasteful number, since it uses less digits than its factorization.

2121780780 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 10516 (or 10511 counting only the distinct ones).

The product of its (nonzero) digits is 12544, while the sum is 36.

The square root of 2121780780 is about 46062.7917087100. The cubic root of 2121780780 is about 1284.9912498710.

The spelling of 2121780780 in words is "two billion, one hundred twenty-one million, seven hundred eighty thousand, seven hundred eighty".