21060780 has 144 divisors (see below), whose sum is σ = 66898944. Its totient is φ = 4942080.

The previous prime is 21060763. The next prime is 21060829. The reversal of 21060780 is 8706012.

It is a self number, because there is not a number n which added to its sum of digits gives 21060780.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 47 ways as a sum of consecutive naturals, for example, 314307 + ... + 314373.

It is an arithmetic number, because the mean of its divisors is an integer number (464576).

Almost surely, 2^21060780 is an apocalyptic number.

21060780 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 21060780, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (33449472).

21060780 is an abundant number, since it is smaller than the sum of its proper divisors (45838164).

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

21060780 is a wasteful number, since it uses less digits than its factorization.

21060780 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 136 (or 121 counting only the distinct ones).

The product of its (nonzero) digits is 672, while the sum is 24.

The square root of 21060780 is about 4589.2025451052. The cubic root of 21060780 is about 276.1583317534.

Adding to 21060780 its reverse (8706012), we get a palindrome (29766792).

The spelling of 21060780 in words is "twenty-one million, sixty thousand, seven hundred eighty".