21281769 has 18 divisors (see below), whose sum is σ = 31277610. Its totient is φ = 13942368.

The previous prime is 21281719. The next prime is 21281783. The reversal of 21281769 is 96718212.

It can be written as a sum of positive squares in only one way, i.e., 15303744 + 5978025 = 3912^2 + 2445^2 .

It is not a de Polignac number, because 21281769 - 2⁷ = 21281641 is a prime.

It is a super-2 number, since 2×21281769² = 905827383538722, which contains 22 as substring.

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (21281719) by changing a digit.

It is a polite number, since it can be written in 17 ways as a sum of consecutive naturals, for example, 130482 + ... + 130644.

It is an arithmetic number, because the mean of its divisors is an integer number (1737645).

Almost surely, 2^21281769 is an apocalyptic number.

It is an amenable number.

21281769 is a deficient number, since it is larger than the sum of its proper divisors (9995841).

21281769 is an equidigital number, since it uses as much as digits as its factorization.

21281769 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 421 (or 255 counting only the distinct ones).

The product of its digits is 12096, while the sum is 36.

The square root of 21281769 is about 4613.2167735757. The cubic root of 21281769 is about 277.1208750133.

The spelling of 21281769 in words is "twenty-one million, two hundred eighty-one thousand, seven hundred sixty-nine".