21551076557 has 4 divisors (see below), whose sum is σ = 21904372956. Its totient is φ = 21197780160.

The previous prime is 21551076551. The next prime is 21551076563. The reversal of 21551076557 is 75567015512.

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

It is an interprime number because it is at equal distance from previous prime (21551076551) and next prime (21551076563).

It can be written as a sum of positive squares in 2 ways, for example, as 2431377481 + 19119699076 = 49309^2 + 138274^2 .

It is a cyclic number.

It is not a de Polignac number, because 21551076557 - 2⁴ = 21551076541 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 (21551076551) 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, 176648108 + ... + 176648229.

It is an arithmetic number, because the mean of its divisors is an integer number (5476093239).

Almost surely, 2^21551076557 is an apocalyptic number.

It is an amenable number.

21551076557 is a deficient number, since it is larger than the sum of its proper divisors (353296399).

21551076557 is an equidigital number, since it uses as much as digits as its factorization.

21551076557 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 353296398.

The product of its (nonzero) digits is 367500, while the sum is 44.

The spelling of 21551076557 in words is "twenty-one billion, five hundred fifty-one million, seventy-six thousand, five hundred fifty-seven".