21566610620 has 24 divisors (see below), whose sum is σ = 45300312288. Its totient is φ = 8624657600.

The previous prime is 21566610587. The next prime is 21566610643. The reversal of 21566610620 is 2601666512.

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 33536 + ... + 210375.

It is an arithmetic number, because the mean of its divisors is an integer number (1887513012).

Almost surely, 2^21566610620 is an apocalyptic number.

21566610620 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21566610620 is an abundant number, since it is smaller than the sum of its proper divisors (23733701668).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

21566610620 is a wasteful number, since it uses less digits than its factorization.

21566610620 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 248341 (or 248339 counting only the distinct ones).

The product of its (nonzero) digits is 25920, while the sum is 35.

The spelling of 21566610620 in words is "twenty-one billion, five hundred sixty-six million, six hundred ten thousand, six hundred twenty".