21528121 has 16 divisors (see below), whose sum is σ = 23760000. Its totient is φ = 19426176.

The previous prime is 21528113. The next prime is 21528127. The reversal of 21528121 is 12182512.

It is a cyclic number.

It is not a de Polignac number, because 21528121 - 2³ = 21528113 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 21528092 and 21528101.

It is not an unprimeable number, because it can be changed into a prime (21528127) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 48820 + ... + 49258.

It is an arithmetic number, because the mean of its divisors is an integer number (1485000).

Almost surely, 2^21528121 is an apocalyptic number.

It is an amenable number.

21528121 is a deficient number, since it is larger than the sum of its proper divisors (2231879).

21528121 is a wasteful number, since it uses less digits than its factorization.

21528121 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 576.

The product of its digits is 320, while the sum is 22.

The square root of 21528121 is about 4639.8406222628. The cubic root of 21528121 is about 278.1860674894.

The spelling of 21528121 in words is "twenty-one million, five hundred twenty-eight thousand, one hundred twenty-one".