21875551 has 4 divisors (see below), whose sum is σ = 21958992. Its totient is φ = 21792112.

The previous prime is 21875543. The next prime is 21875561. The reversal of 21875551 is 15557812.

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 21875551 - 2³ = 21875543 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 (21875561) 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, 41326 + ... + 41851.

It is an arithmetic number, because the mean of its divisors is an integer number (5489748).

Almost surely, 2^21875551 is an apocalyptic number.

21875551 is a deficient number, since it is larger than the sum of its proper divisors (83441).

21875551 is an equidigital number, since it uses as much as digits as its factorization.

21875551 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 83440.

The product of its digits is 14000, while the sum is 34.

The square root of 21875551 is about 4677.1306374742. The cubic root of 21875551 is about 279.6745836820.

The spelling of 21875551 in words is "twenty-one million, eight hundred seventy-five thousand, five hundred fifty-one".