20821538 has 8 divisors (see below), whose sum is σ = 31344300. Its totient is φ = 10373440.

The previous prime is 20821519. The next prime is 20821547. The reversal of 20821538 is 83512802.

It can be written as a sum of positive squares in 2 ways, for example, as 20584369 + 237169 = 4537^2 + 487^2 .

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

It is a self number, because there is not a number n which added to its sum of digits gives 20821538.

It is an unprimeable number.

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 3 ways as a sum of consecutive naturals, for example, 17963 + ... + 19086.

Almost surely, 2^20821538 is an apocalyptic number.

20821538 is a deficient number, since it is larger than the sum of its proper divisors (10522762).

20821538 is a wasteful number, since it uses less digits than its factorization.

20821538 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 37332.

The product of its (nonzero) digits is 3840, while the sum is 29.

The square root of 20821538 is about 4563.0623489056. The cubic root of 20821538 is about 275.1086644943.

The spelling of 20821538 in words is "twenty million, eight hundred twenty-one thousand, five hundred thirty-eight".