21645641 has 8 divisors (see below), whose sum is σ = 23452704. Its totient is φ = 19897920.

The previous prime is 21645619. The next prime is 21645683. The reversal of 21645641 is 14654612.

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 21645641 - 2¹⁸ = 21383497 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21644641) 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, 14075 + ... + 15536.

It is an arithmetic number, because the mean of its divisors is an integer number (2931588).

Almost surely, 2^21645641 is an apocalyptic number.

It is an amenable number.

21645641 is a deficient number, since it is larger than the sum of its proper divisors (1807063).

21645641 is a wasteful number, since it uses less digits than its factorization.

21645641 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 29671.

The product of its digits is 5760, while the sum is 29.

The square root of 21645641 is about 4652.4876141694. The cubic root of 21645641 is about 278.6913464237.

The spelling of 21645641 in words is "twenty-one million, six hundred forty-five thousand, six hundred forty-one".