21421851 has 8 divisors (see below), whose sum is σ = 31159104. Its totient is φ = 12982920.

The previous prime is 21421849. The next prime is 21421861. The reversal of 21421851 is 15812412.

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

It is not a de Polignac number, because 21421851 - 2¹ = 21421849 is a prime.

It is not an unprimeable number, because it can be changed into a prime (21421831) 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, 324541 + ... + 324606.

It is an arithmetic number, because the mean of its divisors is an integer number (3894888).

Almost surely, 2^21421851 is an apocalyptic number.

21421851 is a deficient number, since it is larger than the sum of its proper divisors (9737253).

21421851 is a wasteful number, since it uses less digits than its factorization.

21421851 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 649161.

The product of its digits is 640, while the sum is 24.

The square root of 21421851 is about 4628.3745526913. The cubic root of 21421851 is about 277.7275724317.

It can be divided in two parts, 2142 and 1851, that added together give a palindrome (3993).

The spelling of 21421851 in words is "twenty-one million, four hundred twenty-one thousand, eight hundred fifty-one".