21825865 has 8 divisors (see below), whose sum is σ = 26237448. Its totient is φ = 17429760.

The previous prime is 21825757. The next prime is 21825887. The reversal of 21825865 is 56852812.

It can be written as a sum of positive squares in 4 ways, for example, as 2702736 + 19123129 = 1644^2 + 4373^2 .

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

It is not a de Polignac number, because 21825865 - 2¹⁵ = 21793097 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, 496 + ... + 6625.

It is an arithmetic number, because the mean of its divisors is an integer number (3279681).

Almost surely, 2^21825865 is an apocalyptic number.

It is an amenable number.

21825865 is a deficient number, since it is larger than the sum of its proper divisors (4411583).

21825865 is an equidigital number, since it uses as much as digits as its factorization.

21825865 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 7739.

The product of its digits is 38400, while the sum is 37.

The square root of 21825865 is about 4671.8160280559. The cubic root of 21825865 is about 279.4626812821.

The spelling of 21825865 in words is "twenty-one million, eight hundred twenty-five thousand, eight hundred sixty-five".