21851047 has 4 divisors (see below), whose sum is σ = 22067496. Its totient is φ = 21634600.

The previous prime is 21851041. The next prime is 21851051. The reversal of 21851047 is 74015812.

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

It is a cyclic number.

It is not a de Polignac number, because 21851047 - 2⁷ = 21850919 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 (21851041) 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, 108073 + ... + 108274.

It is an arithmetic number, because the mean of its divisors is an integer number (5516874).

Almost surely, 2^21851047 is an apocalyptic number.

21851047 is a deficient number, since it is larger than the sum of its proper divisors (216449).

21851047 is a wasteful number, since it uses less digits than its factorization.

21851047 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 216448.

The product of its (nonzero) digits is 2240, while the sum is 28.

The square root of 21851047 is about 4674.5103486889. The cubic root of 21851047 is about 279.5701184055.

Adding to 21851047 its reverse (74015812), we get a palindrome (95866859).

The spelling of 21851047 in words is "twenty-one million, eight hundred fifty-one thousand, forty-seven".