21122561780 has 24 divisors (see below), whose sum is σ = 44364194952. Its totient is φ = 8447726592.

The previous prime is 21122561777. The next prime is 21122561807. The reversal of 21122561780 is 8716522112.

It can be written as a sum of positive squares in 4 ways, for example, as 3267722896 + 17854838884 = 57164^2 + 133622^2 .

It is a super-2 number, since 2×21122561780² (a number of 21 digits) contains 22 as substring.

It is a self number, because there is not a number n which added to its sum of digits gives 21122561780.

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 58124 + ... + 213596.

It is an arithmetic number, because the mean of its divisors is an integer number (1848508123).

Almost surely, 2^21122561780 is an apocalyptic number.

21122561780 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21122561780 is an abundant number, since it is smaller than the sum of its proper divisors (23241633172).

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

21122561780 is a wasteful number, since it uses less digits than its factorization.

21122561780 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 162275 (or 162273 counting only the distinct ones).

The product of its (nonzero) digits is 13440, while the sum is 35.

The spelling of 21122561780 in words is "twenty-one billion, one hundred twenty-two million, five hundred sixty-one thousand, seven hundred eighty".