1091978820 has 144 divisors (see below), whose sum is σ = 3584730240. Its totient is φ = 278505216.

The previous prime is 1091978809. The next prime is 1091978821. The reversal of 1091978820 is 288791901.

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

It is not an unprimeable number, because it can be changed into a prime (1091978821) 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, 106896 + ... + 116664.

It is an arithmetic number, because the mean of its divisors is an integer number (24893960).

Almost surely, 2^1091978820 is an apocalyptic number.

1091978820 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 1091978820, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (1792365120).

1091978820 is an abundant number, since it is smaller than the sum of its proper divisors (2492751420).

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

1091978820 is a wasteful number, since it uses less digits than its factorization.

1091978820 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 9816 (or 9802 counting only the distinct ones).

The product of its (nonzero) digits is 72576, while the sum is 45.

The square root of 1091978820 is about 33045.1028141841. The cubic root of 1091978820 is about 1029.7648691921.

The spelling of 1091978820 in words is "one billion, ninety-one million, nine hundred seventy-eight thousand, eight hundred twenty".