21025555621 has 8 divisors (see below), whose sum is σ = 24387851840. Its totient is φ = 17752920768.

The previous prime is 21025555619. The next prime is 21025555631. The reversal of 21025555621 is 12655552012.

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

It is a cyclic number.

It is not a de Polignac number, because 21025555621 - 2¹ = 21025555619 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21025555631) 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, 22414836 + ... + 22415773.

It is an arithmetic number, because the mean of its divisors is an integer number (3048481480).

Almost surely, 2^21025555621 is an apocalyptic number.

It is an amenable number.

21025555621 is a deficient number, since it is larger than the sum of its proper divisors (3362296219).

21025555621 is an equidigital number, since it uses as much as digits as its factorization.

21025555621 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 44830683.

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

The spelling of 21025555621 in words is "twenty-one billion, twenty-five million, five hundred fifty-five thousand, six hundred twenty-one".