21551671 has 2 divisors, whose sum is σ = 21551672. Its totient is φ = 21551670.

The previous prime is 21551657. The next prime is 21551693. The reversal of 21551671 is 17615512.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 21551671 - 2⁵ = 21551639 is a prime.

It is equal to p_1362637 and since 21551671 and 1362637 have the same sum of digits, it is a Honaker prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21551641) 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 as a sum of consecutive naturals, namely, 10775835 + 10775836.

It is an arithmetic number, because the mean of its divisors is an integer number (10775836).

Almost surely, 2^21551671 is an apocalyptic number.

21551671 is a deficient number, since it is larger than the sum of its proper divisors (1).

21551671 is an equidigital number, since it uses as much as digits as its factorization.

21551671 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 2100, while the sum is 28.

The square root of 21551671 is about 4642.3777312924. The cubic root of 21551671 is about 278.2874681099.

It can be divided in two parts, 21551 and 671, that added together give a palindrome (22222).

The spelling of 21551671 in words is "twenty-one million, five hundred fifty-one thousand, six hundred seventy-one".