21153421021 has 8 divisors (see below), whose sum is σ = 21336077880. Its totient is φ = 20971173888.

The previous prime is 21153421001. The next prime is 21153421039. The reversal of 21153421021 is 12012435112.

It can be written as a sum of positive squares in 4 ways, for example, as 4283048025 + 16870372996 = 65445^2 + 129886^2 .

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 21153421021 - 2²³ = 21145032413 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 21153420983 and 21153421001.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21153421001) 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, 1725 + ... + 205693.

It is an arithmetic number, because the mean of its divisors is an integer number (2667009735).

Almost surely, 2^21153421021 is an apocalyptic number.

It is an amenable number.

21153421021 is a deficient number, since it is larger than the sum of its proper divisors (182656859).

21153421021 is a wasteful number, since it uses less digits than its factorization.

21153421021 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 204863.

The product of its (nonzero) digits is 480, while the sum is 22.

Adding to 21153421021 its reverse (12012435112), we get a palindrome (33165856133).

The spelling of 21153421021 in words is "twenty-one billion, one hundred fifty-three million, four hundred twenty-one thousand, twenty-one".