21016720556 has 24 divisors (see below), whose sum is σ = 39720674784. Its totient is φ = 9672537600.

The previous prime is 21016720547. The next prime is 21016720567. The reversal of 21016720556 is 65502761012.

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, 554120 + ... + 590831.

It is an arithmetic number, because the mean of its divisors is an integer number (1655028116).

Almost surely, 2^21016720556 is an apocalyptic number.

21016720556 is a gapful number since it is divisible by the number (26) formed by its first and last digit.

It is an amenable number.

21016720556 is a deficient number, since it is larger than the sum of its proper divisors (18703954228).

21016720556 is a wasteful number, since it uses less digits than its factorization.

21016720556 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1145321 (or 1145319 counting only the distinct ones).

The product of its (nonzero) digits is 25200, while the sum is 35.

The spelling of 21016720556 in words is "twenty-one billion, sixteen million, seven hundred twenty thousand, five hundred fifty-six".