21456766557 has 24 divisors (see below), whose sum is σ = 33071251200. Its totient is φ = 13365995328.

The previous prime is 21456766501. The next prime is 21456766559. The reversal of 21456766557 is 75566765412.

It is a happy number.

21456766557 is a `hidden beast` number, since 2 + 14 + 5 + 6 + 76 + 6 + 557 = 666.

It is not a de Polignac number, because 21456766557 - 2¹² = 21456762461 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21456766559) by changing a digit.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 846957 + ... + 871922.

It is an arithmetic number, because the mean of its divisors is an integer number (1377968800).

Almost surely, 2^21456766557 is an apocalyptic number.

It is an amenable number.

21456766557 is a deficient number, since it is larger than the sum of its proper divisors (11614484643).

21456766557 is a wasteful number, since it uses less digits than its factorization.

21456766557 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1718977 (or 1718974 counting only the distinct ones).

The product of its digits is 10584000, while the sum is 54.

The spelling of 21456766557 in words is "twenty-one billion, four hundred fifty-six million, seven hundred sixty-six thousand, five hundred fifty-seven".