21020855 has 8 divisors (see below), whose sum is σ = 25263600. Its totient is φ = 16790976.

The previous prime is 21020849. The next prime is 21020863. The reversal of 21020855 is 55802012.

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

It is a cyclic number.

It is not a de Polignac number, because 21020855 - 2¹⁴ = 21004471 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 21020855.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 851 + ... + 6539.

It is an arithmetic number, because the mean of its divisors is an integer number (3157950).

Almost surely, 2^21020855 is an apocalyptic number.

21020855 is a deficient number, since it is larger than the sum of its proper divisors (4242745).

21020855 is an equidigital number, since it uses as much as digits as its factorization.

21020855 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 6433.

The product of its (nonzero) digits is 800, while the sum is 23.

The square root of 21020855 is about 4584.8505973477. The cubic root of 21020855 is about 275.9837165707.

Adding to 21020855 its reverse (55802012), we get a palindrome (76822867).

The spelling of 21020855 in words is "twenty-one million, twenty thousand, eight hundred fifty-five".