21661246561544 has 16 divisors (see below), whose sum is σ = 40616000942400. Its totient is φ = 10830312976912.

The previous prime is 21661246561543. The next prime is 21661246561597. The reversal of 21661246561544 is 44516564216612.

It is not an unprimeable number, because it can be changed into a prime (21661246561543) 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, 38491172 + ... + 39049875.

It is an arithmetic number, because the mean of its divisors is an integer number (2538500058900).

Almost surely, 2^{21661246561544} is an apocalyptic number.

It is an amenable number.

21661246561544 is a deficient number, since it is larger than the sum of its proper divisors (18954754380856).

21661246561544 is a wasteful number, since it uses less digits than its factorization.

21661246561544 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 77575972 (or 77575968 counting only the distinct ones).

The product of its digits is 8294400, while the sum is 53.

The spelling of 21661246561544 in words is "twenty-one trillion, six hundred sixty-one billion, two hundred forty-six million, five hundred sixty-one thousand, five hundred forty-four".