21008844661 has 8 divisors (see below), whose sum is σ = 24059012544. Its totient is φ = 17970902880.

The previous prime is 21008844653. The next prime is 21008844707. The reversal of 21008844661 is 16644880012.

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

It is not a de Polignac number, because 21008844661 - 2³ = 21008844653 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21008844601) 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, 3052840 + ... + 3059713.

It is an arithmetic number, because the mean of its divisors is an integer number (3007376568).

Almost surely, 2^21008844661 is an apocalyptic number.

It is an amenable number.

21008844661 is a deficient number, since it is larger than the sum of its proper divisors (3050167883).

21008844661 is an equidigital number, since it uses as much as digits as its factorization.

21008844661 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 6113051.

The product of its (nonzero) digits is 73728, while the sum is 40.

The spelling of 21008844661 in words is "twenty-one billion, eight million, eight hundred forty-four thousand, six hundred sixty-one".