21005351 has 4 divisors (see below), whose sum is σ = 21017304. Its totient is φ = 20993400.

The previous prime is 21005339. The next prime is 21005363. The reversal of 21005351 is 15350012.

It is a semiprime because it is the product of two primes, and also a brilliant number, because the two primes have the same length.

It is an interprime number because it is at equal distance from previous prime (21005339) and next prime (21005363).

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21005351 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 (21005311) 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, 2765 + ... + 7046.

It is an arithmetic number, because the mean of its divisors is an integer number (5254326).

Almost surely, 2^21005351 is an apocalyptic number.

21005351 is a deficient number, since it is larger than the sum of its proper divisors (11953).

21005351 is an equidigital number, since it uses as much as digits as its factorization.

21005351 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 11952.

The product of its (nonzero) digits is 150, while the sum is 17.

The square root of 21005351 is about 4583.1594997338. The cubic root of 21005351 is about 275.9158489866.

Adding to 21005351 its reverse (15350012), we get a palindrome (36355363).

The spelling of 21005351 in words is "twenty-one million, five thousand, three hundred fifty-one".