21661246561542 has 48 divisors (see below), whose sum is σ = 52021216253952. Its totient is φ = 5989284761040.

The previous prime is 21661246561531. The next prime is 21661246561543. The reversal of 21661246561542 is 24516564216612.

It is a congruent number.

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 23 ways as a sum of consecutive naturals, for example, 1188341038 + ... + 1188359265.

It is an arithmetic number, because the mean of its divisors is an integer number (1083775338624).

Almost surely, 2^{21661246561542} is an apocalyptic number.

21661246561542 is an abundant number, since it is smaller than the sum of its proper divisors (30359969692410).

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

21661246561542 is a wasteful number, since it uses less digits than its factorization.

21661246561542 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2376700353 (or 2376700346 counting only the distinct ones).

The product of its digits is 4147200, while the sum is 51.

The spelling of 21661246561542 in words is "twenty-one trillion, six hundred sixty-one billion, two hundred forty-six million, five hundred sixty-one thousand, five hundred forty-two".