21020775 has 12 divisors (see below), whose sum is σ = 34754472. Its totient is φ = 11211040.

The previous prime is 21020761. The next prime is 21020777. The reversal of 21020775 is 57702012.

It is not a de Polignac number, because 21020775 - 2¹³ = 21012583 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21020777) 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, 140064 + ... + 140213.

It is an arithmetic number, because the mean of its divisors is an integer number (2896206).

Almost surely, 2^21020775 is an apocalyptic number.

21020775 is a gapful number since it is divisible by the number (25) formed by its first and last digit.

21020775 is a deficient number, since it is larger than the sum of its proper divisors (13733697).

21020775 is a wasteful number, since it uses less digits than its factorization.

21020775 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 280290 (or 280285 counting only the distinct ones).

The product of its (nonzero) digits is 980, while the sum is 24.

The square root of 21020775 is about 4584.8418729548. The cubic root of 21020775 is about 275.9833664624.

Adding to 21020775 its reverse (57702012), we get a palindrome (78722787).

The spelling of 21020775 in words is "twenty-one million, twenty thousand, seven hundred seventy-five".