21650561 has 8 divisors (see below), whose sum is σ = 21954240. Its totient is φ = 21349008.

The previous prime is 21650539. The next prime is 21650569. The reversal of 21650561 is 16505612.

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

It is a cyclic number.

It is not a de Polignac number, because 21650561 - 2¹⁴ = 21634177 is a prime.

It is a super-2 number, since 2×21650561² = 937493583229442, which contains 22 as substring.

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

It is a Duffinian number.

It is a Curzon number.

It is a self number, because there is not a number n which added to its sum of digits gives 21650561.

It is not an unprimeable number, because it can be changed into a prime (21650569) 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, 33140 + ... + 33786.

It is an arithmetic number, because the mean of its divisors is an integer number (2744280).

Almost surely, 2^21650561 is an apocalyptic number.

It is an amenable number.

21650561 is a deficient number, since it is larger than the sum of its proper divisors (303679).

21650561 is a wasteful number, since it uses less digits than its factorization.

21650561 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1063.

The product of its (nonzero) digits is 1800, while the sum is 26.

The square root of 21650561 is about 4653.0163335196. The cubic root of 21650561 is about 278.7124601058.

The spelling of 21650561 in words is "twenty-one million, six hundred fifty thousand, five hundred sixty-one".