21020364 has 72 divisors (see below), whose sum is σ = 58247280. Its totient is φ = 6532992.

The previous prime is 21020353. The next prime is 21020369. The reversal of 21020364 is 46302012.

It is a happy number.

It is a Harshad number since it is a multiple of its sum of digits (18).

It is not an unprimeable number, because it can be changed into a prime (21020369) by changing a digit.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 196399 + ... + 196505.

It is an arithmetic number, because the mean of its divisors is an integer number (808990).

Almost surely, 2^21020364 is an apocalyptic number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21020364, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (29123640).

21020364 is an abundant number, since it is smaller than the sum of its proper divisors (37226916).

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

21020364 is a wasteful number, since it uses less digits than its factorization.

21020364 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 244 (or 129 counting only the distinct ones).

The product of its (nonzero) digits is 288, while the sum is 18.

The square root of 21020364 is about 4584.7970511245. The cubic root of 21020364 is about 275.9815677672.

Adding to 21020364 its reverse (46302012), we get a palindrome (67322376).

The spelling of 21020364 in words is "twenty-one million, twenty thousand, three hundred sixty-four".