21008121 has 8 divisors (see below), whose sum is σ = 28042080. Its totient is φ = 13989792.

The previous prime is 21008083. The next prime is 21008149. The reversal of 21008121 is 12180012.

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

It is a de Polignac number, because none of the positive numbers 2^k-21008121 is a prime.

It is a super-2 number, since 2×21008121² = 882682295901282, which contains 22 as substring.

It is a self number, because there is not a number n which added to its sum of digits gives 21008121.

It is not an unprimeable number, because it can be changed into a prime (21008171) 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, 291 + ... + 6488.

It is an arithmetic number, because the mean of its divisors is an integer number (3505260).

Almost surely, 2^21008121 is an apocalyptic number.

It is an amenable number.

21008121 is a deficient number, since it is larger than the sum of its proper divisors (7033959).

21008121 is a wasteful number, since it uses less digits than its factorization.

21008121 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 7815.

The product of its (nonzero) digits is 32, while the sum is 15.

The square root of 21008121 is about 4583.4616830514. The cubic root of 21008121 is about 275.9279769012.

Adding to 21008121 its reverse (12180012), we get a palindrome (33188133).

The spelling of 21008121 in words is "twenty-one million, eight thousand, one hundred twenty-one".