20621555521 has 8 divisors (see below), whose sum is σ = 23587124864. Its totient is φ = 17660894400.

The previous prime is 20621555497. The next prime is 20621555527. The reversal of 20621555521 is 12555512602.

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

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-20621555521 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (20621555527) 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, 1218045 + ... + 1234858.

It is an arithmetic number, because the mean of its divisors is an integer number (2948390608).

Almost surely, 2^20621555521 is an apocalyptic number.

It is an amenable number.

20621555521 is a deficient number, since it is larger than the sum of its proper divisors (2965569343).

20621555521 is a wasteful number, since it uses less digits than its factorization.

20621555521 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2454111.

The product of its (nonzero) digits is 30000, while the sum is 34.

The spelling of 20621555521 in words is "twenty billion, six hundred twenty-one million, five hundred fifty-five thousand, five hundred twenty-one".