21560381 has 6 divisors (see below), whose sum is σ = 22160250. Its totient is φ = 20976336.

The previous prime is 21560377. The next prime is 21560387. The reversal of 21560381 is 18306512.

It can be written as a sum of positive squares in 3 ways, for example, as 5480281 + 16080100 = 2341^2 + 4010^2 .

It is not a de Polignac number, because 21560381 - 2² = 21560377 is a prime.

It is a super-2 number, since 2×21560381² = 929700057730322, which contains 22 as substring.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 21560381.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21560387) by changing a digit.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 6506 + ... + 9243.

It is an arithmetic number, because the mean of its divisors is an integer number (3693375).

Almost surely, 2^21560381 is an apocalyptic number.

It is an amenable number.

21560381 is a deficient number, since it is larger than the sum of its proper divisors (599869).

21560381 is an equidigital number, since it uses as much as digits as its factorization.

21560381 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 15823 (or 15786 counting only the distinct ones).

The product of its (nonzero) digits is 1440, while the sum is 26.

The square root of 21560381 is about 4643.3157333957. The cubic root of 21560381 is about 278.3249525566.

Adding to 21560381 its reverse (18306512), we get a palindrome (39866893).

The spelling of 21560381 in words is "twenty-one million, five hundred sixty thousand, three hundred eighty-one".