1221087820 has 48 divisors (see below), whose sum is σ = 2737324800. Its totient is φ = 456200640.

The previous prime is 1221087809. The next prime is 1221087821. The reversal of 1221087820 is 287801221.

It is not an unprimeable number, because it can be changed into a prime (1221087821) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 4351 + ... + 49609.

It is an arithmetic number, because the mean of its divisors is an integer number (57027600).

Almost surely, 2^1221087820 is an apocalyptic number.

1221087820 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 1221087820, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (1368662400).

1221087820 is an abundant number, since it is smaller than the sum of its proper divisors (1516236980).

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

1221087820 is a wasteful number, since it uses less digits than its factorization.

1221087820 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 45358 (or 45356 counting only the distinct ones).

The product of its (nonzero) digits is 3584, while the sum is 31.

The square root of 1221087820 is about 34944.0670214559. The cubic root of 1221087820 is about 1068.8472226911.

The spelling of 1221087820 in words is "one billion, two hundred twenty-one million, eighty-seven thousand, eight hundred twenty".