21055557787 has 8 divisors (see below), whose sum is σ = 23134950720. Its totient is φ = 19003706760.

The previous prime is 21055557779. The next prime is 21055557797. The reversal of 21055557787 is 78775555012.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 21055557787 - 2³ = 21055557779 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21055557707) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 6883873 + ... + 6886930.

It is an arithmetic number, because the mean of its divisors is an integer number (2891868840).

Almost surely, 2^21055557787 is an apocalyptic number.

21055557787 is a deficient number, since it is larger than the sum of its proper divisors (2079392933).

21055557787 is a wasteful number, since it uses less digits than its factorization.

21055557787 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 13770953.

The product of its (nonzero) digits is 3430000, while the sum is 52.

The spelling of 21055557787 in words is "twenty-one billion, fifty-five million, five hundred fifty-seven thousand, seven hundred eighty-seven".