21661521954554 has 8 divisors (see below), whose sum is σ = 32497884101268. Its totient is φ = 10828893920800.

The previous prime is 21661521954551. The next prime is 21661521954563. The reversal of 21661521954554 is 45545912516612.

It can be written as a sum of positive squares in 2 ways, for example, as 13278626680225 + 8382895274329 = 3643985^2 + 2895323^2 .

It is a sphenic number, since it is the product of 3 distinct primes.

It is a Curzon number.

It is a self number, because there is not a number n which added to its sum of digits gives 21661521954554.

It is not an unprimeable number, because it can be changed into a prime (21661521954551) 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, 933513737 + ... + 933536940.

Almost surely, 2^{21661521954554} is an apocalyptic number.

21661521954554 is a deficient number, since it is larger than the sum of its proper divisors (10836362146714).

21661521954554 is a wasteful number, since it uses less digits than its factorization.

21661521954554 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1867056480.

The product of its digits is 12960000, while the sum is 56.

The spelling of 21661521954554 in words is "twenty-one trillion, six hundred sixty-one billion, five hundred twenty-one million, nine hundred fifty-four thousand, five hundred fifty-four".