20821638 has 16 divisors (see below), whose sum is σ = 41878080. Its totient is φ = 6901416.

The previous prime is 20821637. The next prime is 20821643. The reversal of 20821638 is 83612802.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (20821637) 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, 8620 + ... + 10767.

It is an arithmetic number, because the mean of its divisors is an integer number (2617380).

Almost surely, 2^20821638 is an apocalyptic number.

20821638 is an abundant number, since it is smaller than the sum of its proper divisors (21056442).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

20821638 is a wasteful number, since it uses less digits than its factorization.

20821638 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 19571.

The product of its (nonzero) digits is 4608, while the sum is 30.

The square root of 20821638 is about 4563.0733064460. The cubic root of 20821638 is about 275.1091049168.

The spelling of 20821638 in words is "twenty million, eight hundred twenty-one thousand, six hundred thirty-eight".