20528991 has 48 divisors (see below), whose sum is σ = 36115200. Its totient is φ = 11488176.

The previous prime is 20528947. The next prime is 20528993. The reversal of 20528991 is 19982502.

It is not a de Polignac number, because 20528991 - 2⁷ = 20528863 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (20528993) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 47 ways as a sum of consecutive naturals, for example, 77926 + ... + 78188.

It is an arithmetic number, because the mean of its divisors is an integer number (752400).

Almost surely, 2^20528991 is an apocalyptic number.

20528991 is a gapful number since it is divisible by the number (21) formed by its first and last digit.

20528991 is a deficient number, since it is larger than the sum of its proper divisors (15586209).

20528991 is a wasteful number, since it uses less digits than its factorization.

20528991 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 345 (or 332 counting only the distinct ones).

The product of its (nonzero) digits is 12960, while the sum is 36.

The square root of 20528991 is about 4530.8929583472. The cubic root of 20528991 is about 273.8141377209.

The spelling of 20528991 in words is "twenty million, five hundred twenty-eight thousand, nine hundred ninety-one".