21661042216556 has 12 divisors (see below), whose sum is σ = 37907854801320. Its totient is φ = 10830226559040.

The previous prime is 21661042216553. The next prime is 21661042216571. The reversal of 21661042216556 is 65561224016612.

It is a super-2 number, since 2×21661042216556² (a number of 27 digits) contains 22 as substring.

It is a self number, because there is not a number n which added to its sum of digits gives 21661042216556.

It is not an unprimeable number, because it can be changed into a prime (21661042216553) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 73471805 + ... + 73766036.

It is an arithmetic number, because the mean of its divisors is an integer number (3158987900110).

Almost surely, 2^{21661042216556} is an apocalyptic number.

It is an amenable number.

21661042216556 is a deficient number, since it is larger than the sum of its proper divisors (16246812584764).

21661042216556 is a wasteful number, since it uses less digits than its factorization.

21661042216556 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 147274624 (or 147274622 counting only the distinct ones).

The product of its (nonzero) digits is 1036800, while the sum is 47.

The spelling of 21661042216556 in words is "twenty-one trillion, six hundred sixty-one billion, forty-two million, two hundred sixteen thousand, five hundred fifty-six".