21020051 has 12 divisors (see below), whose sum is σ = 23145840. Its totient is φ = 19075680.

The previous prime is 21020039. The next prime is 21020053. The reversal of 21020051 is 15002012.

It is not a de Polignac number, because 21020051 - 2⁶ = 21019987 is a prime.

It is not an unprimeable number, because it can be changed into a prime (21020053) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 9290 + ... + 11328.

It is an arithmetic number, because the mean of its divisors is an integer number (1928820).

Almost surely, 2^21020051 is an apocalyptic number.

21020051 is a deficient number, since it is larger than the sum of its proper divisors (2125789).

21020051 is a wasteful number, since it uses less digits than its factorization.

21020051 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2126 (or 2113 counting only the distinct ones).

The product of its (nonzero) digits is 20, while the sum is 11.

The square root of 21020051 is about 4584.7629164440. The cubic root of 21020051 is about 275.9801979422.

Adding to 21020051 its reverse (15002012), we get a palindrome (36022063).

The spelling of 21020051 in words is "twenty-one million, twenty thousand, fifty-one".