21279845 has 6 divisors (see below), whose sum is σ = 25548198. Its totient is φ = 17015624.

The previous prime is 21279833. The next prime is 21279851. The reversal of 21279845 is 54897212.

It can be written as a sum of positive squares in only one way, i.e., 17023876 + 4255969 = 4126^2 + 2063^2 .

It is not a de Polignac number, because 21279845 - 2⁶ = 21279781 is a prime.

It is a Duffinian number.

It is a Curzon number.

It is a junction number, because it is equal to n+sod(n) for n = 21279799 and 21279808.

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 9284 + ... + 11346.

It is an arithmetic number, because the mean of its divisors is an integer number (4258033).

Almost surely, 2^21279845 is an apocalyptic number.

It is an amenable number.

21279845 is a deficient number, since it is larger than the sum of its proper divisors (4268353).

21279845 is an frugal number, since it uses more digits than its factorization.

21279845 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 4131 (or 2068 counting only the distinct ones).

The product of its digits is 40320, while the sum is 38.

The square root of 21279845 is about 4613.0082375821. The cubic root of 21279845 is about 277.1125236300.

The spelling of 21279845 in words is "twenty-one million, two hundred seventy-nine thousand, eight hundred forty-five".