2121561900 has 108 divisors (see below), whose sum is σ = 6664849464. Its totient is φ = 564480000.

The previous prime is 2121561887. The next prime is 2121561917. The reversal of 2121561900 is 91651212.

2121561900 is a `hidden beast` number, since 2 + 12 + 1 + 561 + 90 + 0 = 666.

It is a super-2 number, since 2×2121561900² = 9002049791063220000, which contains 22 as substring.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 35 ways as a sum of consecutive naturals, for example, 439500 + ... + 444300.

Almost surely, 2^2121561900 is an apocalyptic number.

2121561900 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 2121561900, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (3332424732).

2121561900 is an abundant number, since it is smaller than the sum of its proper divisors (4543287564).

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

2121561900 is a wasteful number, since it uses less digits than its factorization.

2121561900 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 5312 (or 5302 counting only the distinct ones).

The product of its (nonzero) digits is 1080, while the sum is 27.

The square root of 2121561900 is about 46060.4157601731. The cubic root of 2121561900 is about 1284.9470623723.

The spelling of 2121561900 in words is "two billion, one hundred twenty-one million, five hundred sixty-one thousand, nine hundred".