21220775 has 12 divisors (see below), whose sum is σ = 26563032. Its totient is φ = 16815840.

The previous prime is 21220757. The next prime is 21220783. The reversal of 21220775 is 57702212.

It is not a de Polignac number, because 21220775 - 2⁶ = 21220711 is a prime.

It is a Duffinian number.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 1292 + ... + 6641.

It is an arithmetic number, because the mean of its divisors is an integer number (2213586).

Almost surely, 2^21220775 is an apocalyptic number.

21220775 is a gapful number since it is divisible by the number (25) formed by its first and last digit.

21220775 is a deficient number, since it is larger than the sum of its proper divisors (5342257).

21220775 is a wasteful number, since it uses less digits than its factorization.

21220775 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 8050 (or 8045 counting only the distinct ones).

The product of its (nonzero) digits is 1960, while the sum is 26.

The square root of 21220775 is about 4606.6012416965. The cubic root of 21220775 is about 276.8558769258.

Adding to 21220775 its reverse (57702212), we get a palindrome (78922987).

The spelling of 21220775 in words is "twenty-one million, two hundred twenty thousand, seven hundred seventy-five".