21032561 has 8 divisors (see below), whose sum is σ = 23065824. Its totient is φ = 19019520.

The previous prime is 21032537. The next prime is 21032567. The reversal of 21032561 is 16523012.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21032561 is a prime.

It is an alternating number because its digits alternate between even and odd.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21032567) 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, 2831 + ... + 7076.

It is an arithmetic number, because the mean of its divisors is an integer number (2883228).

Almost surely, 2^21032561 is an apocalyptic number.

It is an amenable number.

21032561 is a deficient number, since it is larger than the sum of its proper divisors (2033263).

21032561 is a wasteful number, since it uses less digits than its factorization.

21032561 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 10111.

The product of its (nonzero) digits is 360, while the sum is 20.

The square root of 21032561 is about 4586.1270152494. The cubic root of 21032561 is about 276.0349365913.

Adding to 21032561 its reverse (16523012), we get a palindrome (37555573).

It can be divided in two parts, 2103 and 2561, that added together give a palindrome (4664).

The spelling of 21032561 in words is "twenty-one million, thirty-two thousand, five hundred sixty-one".