21741661 has 4 divisors (see below), whose sum is σ = 21765024. Its totient is φ = 21718300.

The previous prime is 21741659. The next prime is 21741667. The reversal of 21741661 is 16614712.

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 21741661 - 2¹ = 21741659 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21741667) 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, 10225 + ... + 12166.

It is an arithmetic number, because the mean of its divisors is an integer number (5441256).

Almost surely, 2^21741661 is an apocalyptic number.

It is an amenable number.

21741661 is a deficient number, since it is larger than the sum of its proper divisors (23363).

21741661 is an equidigital number, since it uses as much as digits as its factorization.

21741661 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 23362.

The product of its digits is 2016, while the sum is 28.

The square root of 21741661 is about 4662.7954061914. The cubic root of 21741661 is about 279.1028299075.

The spelling of 21741661 in words is "twenty-one million, seven hundred forty-one thousand, six hundred sixty-one".