21155230021 has 8 divisors (see below), whose sum is σ = 22270360320. Its totient is φ = 20040269472.

The previous prime is 21155230013. The next prime is 21155230027. The reversal of 21155230021 is 12003255112.

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 21155230021 - 2³ = 21155230013 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 21155229974 and 21155230001.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21155230027) 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, 273921 + ... + 342553.

It is an arithmetic number, because the mean of its divisors is an integer number (2783795040).

Almost surely, 2^21155230021 is an apocalyptic number.

It is an amenable number.

21155230021 is a deficient number, since it is larger than the sum of its proper divisors (1115130299).

21155230021 is a wasteful number, since it uses less digits than its factorization.

21155230021 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 84875.

The product of its (nonzero) digits is 600, while the sum is 22.

Adding to 21155230021 its reverse (12003255112), we get a palindrome (33158485133).

The spelling of 21155230021 in words is "twenty-one billion, one hundred fifty-five million, two hundred thirty thousand, twenty-one".