21557671 has 2 divisors, whose sum is σ = 21557672. Its totient is φ = 21557670.

The previous prime is 21557651. The next prime is 21557681. The reversal of 21557671 is 17675512.

It is a happy number.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 21557671 - 2⁵ = 21557639 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21557621) 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, 10778835 + 10778836.

It is an arithmetic number, because the mean of its divisors is an integer number (10778836).

Almost surely, 2^21557671 is an apocalyptic number.

21557671 is a deficient number, since it is larger than the sum of its proper divisors (1).

21557671 is an equidigital number, since it uses as much as digits as its factorization.

21557671 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 14700, while the sum is 34.

The square root of 21557671 is about 4643.0239068952. The cubic root of 21557671 is about 278.3132908544.

The spelling of 21557671 in words is "twenty-one million, five hundred fifty-seven thousand, six hundred seventy-one".