21079745 has 8 divisors (see below), whose sum is σ = 26783784. Its totient is φ = 15871744.

The previous prime is 21079727. The next prime is 21079769. The reversal of 21079745 is 54797012.

It can be written as a sum of positive squares in 4 ways, for example, as 1825201 + 19254544 = 1351^2 + 4388^2 .

It is a sphenic number, since it is the product of 3 distinct primes.

It is not a de Polignac number, because 21079745 - 2²⁰ = 20031169 is a prime.

It is a Duffinian number.

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 123914 + ... + 124083.

It is an arithmetic number, because the mean of its divisors is an integer number (3347973).

Almost surely, 2^21079745 is an apocalyptic number.

It is an amenable number.

21079745 is a deficient number, since it is larger than the sum of its proper divisors (5704039).

21079745 is a wasteful number, since it uses less digits than its factorization.

21079745 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 248019.

The product of its (nonzero) digits is 17640, while the sum is 35.

The square root of 21079745 is about 4591.2683432794. The cubic root of 21079745 is about 276.2411993948.

The spelling of 21079745 in words is "twenty-one million, seventy-nine thousand, seven hundred forty-five".