21056351 has 4 divisors (see below), whose sum is σ = 22164600. Its totient is φ = 19948104.

The previous prime is 21056311. The next prime is 21056363. The reversal of 21056351 is 15365012.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21056351 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 (21056311) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 554096 + ... + 554133.

It is an arithmetic number, because the mean of its divisors is an integer number (5541150).

Almost surely, 2^21056351 is an apocalyptic number.

21056351 is a deficient number, since it is larger than the sum of its proper divisors (1108249).

21056351 is a wasteful number, since it uses less digits than its factorization.

21056351 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1108248.

The product of its (nonzero) digits is 900, while the sum is 23.

The square root of 21056351 is about 4588.7199740233. The cubic root of 21056351 is about 276.1389720558.

The spelling of 21056351 in words is "twenty-one million, fifty-six thousand, three hundred fifty-one".