21010556623 has 4 divisors (see below), whose sum is σ = 24012064720. Its totient is φ = 18009048528.

The previous prime is 21010556617. The next prime is 21010556639. The reversal of 21010556623 is 32665501012.

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

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21010556623 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21010556423) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 1500754038 + ... + 1500754051.

It is an arithmetic number, because the mean of its divisors is an integer number (6003016180).

Almost surely, 2^21010556623 is an apocalyptic number.

21010556623 is a deficient number, since it is larger than the sum of its proper divisors (3001508097).

21010556623 is an equidigital number, since it uses as much as digits as its factorization.

21010556623 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3001508096.

The product of its (nonzero) digits is 10800, while the sum is 31.

The spelling of 21010556623 in words is "twenty-one billion, ten million, five hundred fifty-six thousand, six hundred twenty-three".