21661020453542 has 16 divisors (see below), whose sum is σ = 32708798576640. Its totient is φ = 10758160494792.

The previous prime is 21661020453503. The next prime is 21661020453551. The reversal of 21661020453542 is 24535402016612.

It is a self number, because there is not a number n which added to its sum of digits gives 21661020453542.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 17629742 + ... + 18818337.

It is an arithmetic number, because the mean of its divisors is an integer number (2044299911040).

Almost surely, 2^{21661020453542} is an apocalyptic number.

21661020453542 is a deficient number, since it is larger than the sum of its proper divisors (11047778123098).

21661020453542 is a wasteful number, since it uses less digits than its factorization.

21661020453542 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 36450067.

The product of its (nonzero) digits is 345600, while the sum is 41.

The spelling of 21661020453542 in words is "twenty-one trillion, six hundred sixty-one billion, twenty million, four hundred fifty-three thousand, five hundred forty-two".