21121051521 has 8 divisors (see below), whose sum is σ = 28193154624. Its totient is φ = 14064824720.

The previous prime is 21121051513. The next prime is 21121051537. The reversal of 21121051521 is 12515012112.

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 21121051521 - 2³ = 21121051513 is a prime.

It is not an unprimeable number, because it can be changed into a prime (21121051541) 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, 3965970 + ... + 3971291.

It is an arithmetic number, because the mean of its divisors is an integer number (3524144328).

Almost surely, 2^21121051521 is an apocalyptic number.

It is an amenable number.

21121051521 is a deficient number, since it is larger than the sum of its proper divisors (7072103103).

21121051521 is an equidigital number, since it uses as much as digits as its factorization.

21121051521 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 7938151.

The product of its (nonzero) digits is 200, while the sum is 21.

Adding to 21121051521 its reverse (12515012112), we get a palindrome (33636063633).

The spelling of 21121051521 in words is "twenty-one billion, one hundred twenty-one million, fifty-one thousand, five hundred twenty-one".