21070780 has 12 divisors (see below), whose sum is σ = 44248680. Its totient is φ = 8428304.

The previous prime is 21070759. The next prime is 21070781. The reversal of 21070780 is 8707012.

It is a happy number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21070781) by changing a digit.

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 3 ways as a sum of consecutive naturals, for example, 526750 + ... + 526789.

It is an arithmetic number, because the mean of its divisors is an integer number (3687390).

Almost surely, 2^21070780 is an apocalyptic number.

21070780 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21070780 is an abundant number, since it is smaller than the sum of its proper divisors (23177900).

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

21070780 is a wasteful number, since it uses less digits than its factorization.

21070780 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1053548 (or 1053546 counting only the distinct ones).

The product of its (nonzero) digits is 784, while the sum is 25.

The square root of 21070780 is about 4590.2919297143. The cubic root of 21070780 is about 276.2020329894.

Adding to 21070780 its reverse (8707012), we get a palindrome (29777792).

The spelling of 21070780 in words is "twenty-one million, seventy thousand, seven hundred eighty".