21016580 has 24 divisors (see below), whose sum is σ = 47530392. Its totient is φ = 7759872.

The previous prime is 21016577. The next prime is 21016601. The reversal of 21016580 is 8561012.

It can be written as a sum of positive squares in 4 ways, for example, as 350464 + 20666116 = 592^2 + 4546^2 .

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 40157 + ... + 40676.

It is an arithmetic number, because the mean of its divisors is an integer number (1980433).

Almost surely, 2^21016580 is an apocalyptic number.

21016580 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21016580 is an abundant number, since it is smaller than the sum of its proper divisors (26513812).

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

21016580 is a wasteful number, since it uses less digits than its factorization.

21016580 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 80855 (or 80853 counting only the distinct ones).

The product of its (nonzero) digits is 480, while the sum is 23.

The square root of 21016580 is about 4584.3843643394. The cubic root of 21016580 is about 275.9650064155.

Adding to 21016580 its reverse (8561012), we get a palindrome (29577592).

The spelling of 21016580 in words is "twenty-one million, sixteen thousand, five hundred eighty".