2121561660 has 48 divisors (see below), whose sum is σ = 6253027200. Its totient is φ = 535973184.

The previous prime is 2121561647. The next prime is 2121561677. The reversal of 2121561660 is 661651212.

It is a Harshad number since it is a multiple of its sum of digits (30).

It is a congruent number.

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 15 ways as a sum of consecutive naturals, for example, 929370 + ... + 931649.

It is an arithmetic number, because the mean of its divisors is an integer number (130271400).

Almost surely, 2^2121561660 is an apocalyptic number.

2121561660 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

2121561660 is an abundant number, since it is smaller than the sum of its proper divisors (4131465540).

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

2121561660 is a wasteful number, since it uses less digits than its factorization.

2121561660 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1861050 (or 1861048 counting only the distinct ones).

The product of its (nonzero) digits is 4320, while the sum is 30.

The square root of 2121561660 is about 46060.4131548991. The cubic root of 2121561660 is about 1284.9470139194.

The spelling of 2121561660 in words is "two billion, one hundred twenty-one million, five hundred sixty-one thousand, six hundred sixty".