21325561 has 4 divisors (see below), whose sum is σ = 21340800. Its totient is φ = 21310324.

The previous prime is 21325553. The next prime is 21325567. The reversal of 21325561 is 16552312.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 21325561 - 2³ = 21325553 is a prime.

It is a Duffinian number.

It is a plaindrome in base 13.

It is not an unprimeable number, because it can be changed into a prime (21325567) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 5281 + ... + 8398.

It is an arithmetic number, because the mean of its divisors is an integer number (5335200).

Almost surely, 2^21325561 is an apocalyptic number.

It is an amenable number.

21325561 is a deficient number, since it is larger than the sum of its proper divisors (15239).

21325561 is a wasteful number, since it uses less digits than its factorization.

21325561 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 15238.

The product of its digits is 1800, while the sum is 25.

The square root of 21325561 is about 4617.9606971043. The cubic root of 21325561 is about 277.3108241807.

Adding to 21325561 its reverse (16552312), we get a palindrome (37877873).

The spelling of 21325561 in words is "twenty-one million, three hundred twenty-five thousand, five hundred sixty-one".