21579745 has 24 divisors (see below), whose sum is σ = 29044008. Its totient is φ = 15375360.

The previous prime is 21579737. The next prime is 21579791. The reversal of 21579745 is 54797512.

It can be written as a sum of positive squares in 4 ways, for example, as 2509056 + 19070689 = 1584^2 + 4367^2 .

It is not a de Polignac number, because 21579745 - 2³ = 21579737 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 21579698 and 21579707.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 31729 + ... + 32401.

It is an arithmetic number, because the mean of its divisors is an integer number (1210167).

Almost surely, 2^21579745 is an apocalyptic number.

It is an amenable number.

21579745 is a deficient number, since it is larger than the sum of its proper divisors (7464263).

21579745 is a wasteful number, since it uses less digits than its factorization.

21579745 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 753 (or 742 counting only the distinct ones).

The product of its digits is 88200, while the sum is 40.

The square root of 21579745 is about 4645.4004133121. The cubic root of 21579745 is about 278.4082515129.

It can be divided in two parts, 21 and 579745, that multiplied together give a triangular number (12174645 = T₄₉₃₄).

The spelling of 21579745 in words is "twenty-one million, five hundred seventy-nine thousand, seven hundred forty-five".