21016560 has 80 divisors (see below), whose sum is σ = 66174336. Its totient is φ = 5516544.

The previous prime is 21016547. The next prime is 21016577. The reversal of 21016560 is 6561012.

It is a happy number.

It is a tau number, because it is divible by the number of its divisors (80).

It is a zygodrome in base 4.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 15427 + ... + 16733.

Almost surely, 2^21016560 is an apocalyptic number.

21016560 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 21016560, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (33087168).

21016560 is an abundant number, since it is smaller than the sum of its proper divisors (45157776).

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

21016560 is a wasteful number, since it uses less digits than its factorization.

21016560 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1390 (or 1384 counting only the distinct ones).

The product of its (nonzero) digits is 360, while the sum is 21.

The square root of 21016560 is about 4584.3821830210. The cubic root of 21016560 is about 275.9649188766.

Adding to 21016560 its reverse (6561012), we get a palindrome (27577572).

The spelling of 21016560 in words is "twenty-one million, sixteen thousand, five hundred sixty".