21005601 has 8 divisors (see below), whose sum is σ = 29225280. Its totient is φ = 13394832.

The previous prime is 21005597. The next prime is 21005609. The reversal of 21005601 is 10650012.

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

It is not a de Polignac number, because 21005601 - 2² = 21005597 is a prime.

It is not an unprimeable number, because it can be changed into a prime (21005609) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (7) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 152146 + ... + 152283.

It is an arithmetic number, because the mean of its divisors is an integer number (3653160).

Almost surely, 2^21005601 is an apocalyptic number.

It is an amenable number.

21005601 is a deficient number, since it is larger than the sum of its proper divisors (8219679).

21005601 is a wasteful number, since it uses less digits than its factorization.

21005601 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 304455.

The product of its (nonzero) digits is 60, while the sum is 15.

The square root of 21005601 is about 4583.1867734143. The cubic root of 21005601 is about 275.9169436075.

Adding to 21005601 its reverse (10650012), we get a palindrome (31655613).

The spelling of 21005601 in words is "twenty-one million, five thousand, six hundred one".