21730661 has 4 divisors (see below), whose sum is σ = 22874400. Its totient is φ = 20586924.

The previous prime is 21730649. The next prime is 21730663. The reversal of 21730661 is 16603712.

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 21730661 - 2¹⁰ = 21729637 is a prime.

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 21730661.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21730663) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 571841 + ... + 571878.

It is an arithmetic number, because the mean of its divisors is an integer number (5718600).

Almost surely, 2^21730661 is an apocalyptic number.

It is an amenable number.

21730661 is a deficient number, since it is larger than the sum of its proper divisors (1143739).

21730661 is a wasteful number, since it uses less digits than its factorization.

21730661 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1143738.

The product of its (nonzero) digits is 1512, while the sum is 26.

The square root of 21730661 is about 4661.6157070269. The cubic root of 21730661 is about 279.0557521023.

The spelling of 21730661 in words is "twenty-one million, seven hundred thirty thousand, six hundred sixty-one".