21025825 has 24 divisors (see below), whose sum is σ = 27170136. Its totient is φ = 16128000.

The previous prime is 21025819. The next prime is 21025831. The reversal of 21025825 is 52852012.

It is an interprime number because it is at equal distance from previous prime (21025819) and next prime (21025831).

It can be written as a sum of positive squares in 12 ways, for example, as 8579041 + 12446784 = 2929^2 + 3528^2 .

It is not a de Polignac number, because 21025825 - 2⁵ = 21025793 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (25).

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 21025825.

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, 74685 + ... + 74965.

It is an arithmetic number, because the mean of its divisors is an integer number (1132089).

Almost surely, 2^21025825 is an apocalyptic number.

21025825 is a gapful number since it is divisible by the number (25) formed by its first and last digit.

It is an amenable number.

21025825 is a deficient number, since it is larger than the sum of its proper divisors (6144311).

21025825 is a wasteful number, since it uses less digits than its factorization.

21025825 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 405 (or 400 counting only the distinct ones).

The product of its (nonzero) digits is 1600, while the sum is 25.

The square root of 21025825 is about 4585.3925677089. The cubic root of 21025825 is about 276.0054653052.

Adding to 21025825 its reverse (52852012), we get a palindrome (73877837).

The spelling of 21025825 in words is "twenty-one million, twenty-five thousand, eight hundred twenty-five".