2121023556 has 72 divisors (see below), whose sum is σ = 5643208480. Its totient is φ = 696434112.

The previous prime is 2121023551. The next prime is 2121023563. The reversal of 2121023556 is 6553201212.

It is a happy number.

2121023556 is a `hidden beast` number, since 2 + 1 + 2 + 102 + 3 + 556 = 666.

It is a Harshad number since it is a multiple of its sum of digits (27).

It is not an unprimeable number, because it can be changed into a prime (2121023551) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 48840 + ... + 81408.

Almost surely, 2^2121023556 is an apocalyptic number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 2121023556, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (2821604240).

2121023556 is an abundant number, since it is smaller than the sum of its proper divisors (3522184924).

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

2121023556 is a wasteful number, since it uses less digits than its factorization.

2121023556 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 32655 (or 32641 counting only the distinct ones).

The product of its (nonzero) digits is 3600, while the sum is 27.

The square root of 2121023556 is about 46054.5714994722. The cubic root of 2121023556 is about 1284.8383685432.

Adding to 2121023556 its reverse (6553201212), we get a palindrome (8674224768).

The spelling of 2121023556 in words is "two billion, one hundred twenty-one million, twenty-three thousand, five hundred fifty-six".