21081560 has 32 divisors (see below), whose sum is σ = 47792160. Its totient is φ = 8368896.

The previous prime is 21081559. The next prime is 21081569. The reversal of 21081560 is 6518012.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21081569) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 3557 + ... + 7403.

It is an arithmetic number, because the mean of its divisors is an integer number (1493505).

Almost surely, 2^21081560 is an apocalyptic number.

21081560 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21081560 is an abundant number, since it is smaller than the sum of its proper divisors (26710600).

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

21081560 is a wasteful number, since it uses less digits than its factorization.

21081560 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3995 (or 3991 counting only the distinct ones).

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

The square root of 21081560 is about 4591.4659968250. The cubic root of 21081560 is about 276.2491274380.

Adding to 21081560 its reverse (6518012), we get a palindrome (27599572).

The spelling of 21081560 in words is "twenty-one million, eighty-one thousand, five hundred sixty".