20529821 has 4 divisors (see below), whose sum is σ = 22109052. Its totient is φ = 18950592.

The previous prime is 20529799. The next prime is 20529851. The reversal of 20529821 is 12892502.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 13586596 + 6943225 = 3686^2 + 2635^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-20529821 is a prime.

It is a Duffinian number.

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (20529851) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 789596 + ... + 789621.

It is an arithmetic number, because the mean of its divisors is an integer number (5527263).

Almost surely, 2^20529821 is an apocalyptic number.

It is an amenable number.

20529821 is a deficient number, since it is larger than the sum of its proper divisors (1579231).

20529821 is a wasteful number, since it uses less digits than its factorization.

20529821 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1579230.

The product of its (nonzero) digits is 2880, while the sum is 29.

The square root of 20529821 is about 4530.9845508454. The cubic root of 20529821 is about 273.8178278304.

The spelling of 20529821 in words is "twenty million, five hundred twenty-nine thousand, eight hundred twenty-one".