21081780420100 has 81 divisors (see below), whose sum is σ = 47825358501333. Its totient is φ = 8065668457440.

The previous prime is 21081780420053. The next prime is 21081780420133. The reversal of 21081780420100 is 102408718012.

The square root of 21081780420100 is 4591490.

It is a perfect power (a square), and thus also a powerful number.

It can be written as a sum of positive squares in only one way, i.e., 7589440951236 + 13492339468864 = 2754894^2 + 3673192^2 .

It is a Duffinian 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 26 ways as a sum of consecutive naturals, for example, 1056032719 + ... + 1056052681.

Almost surely, 2^{21081780420100} is an apocalyptic number.

21081780420100 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

21081780420100 is the 4591490-th square number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21081780420100

21081780420100 is an abundant number, since it is smaller than the sum of its proper divisors (26743578081233).

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

21081780420100 is an frugal number, since it uses more digits than its factorization.

21081780420100 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 39986 (or 19993 counting only the distinct ones).

The product of its (nonzero) digits is 7168, while the sum is 34.

The spelling of 21081780420100 in words is "twenty-one trillion, eighty-one billion, seven hundred eighty million, four hundred twenty thousand, one hundred".