21661530621 has 8 divisors (see below), whose sum is σ = 30402148320. Its totient is φ = 13680966672.

The previous prime is 21661530589. The next prime is 21661530629. The reversal of 21661530621 is 12603516612.

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

It is not a de Polignac number, because 21661530621 - 2⁵ = 21661530589 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21661530629) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 190013370 + ... + 190013483.

It is an arithmetic number, because the mean of its divisors is an integer number (3800268540).

Almost surely, 2^21661530621 is an apocalyptic number.

It is an amenable number.

21661530621 is a deficient number, since it is larger than the sum of its proper divisors (8740617699).

21661530621 is a wasteful number, since it uses less digits than its factorization.

21661530621 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 380026875.

The product of its (nonzero) digits is 12960, while the sum is 33.

The spelling of 21661530621 in words is "twenty-one billion, six hundred sixty-one million, five hundred thirty thousand, six hundred twenty-one".