21020825 has 24 divisors (see below), whose sum is σ = 30081408. Its totient is φ = 14273280.

The previous prime is 21020819. The next prime is 21020837. The reversal of 21020825 is 52802012.

It is not a de Polignac number, because 21020825 - 2⁶ = 21020761 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 21020797 and 21020806.

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, 19244 + ... + 20306.

It is an arithmetic number, because the mean of its divisors is an integer number (1253392).

Almost surely, 2^21020825 is an apocalyptic number.

21020825 is a gapful number since it is divisible by the number (25) formed by its first and last digit.

It is an amenable number.

21020825 is a deficient number, since it is larger than the sum of its proper divisors (9060583).

21020825 is a wasteful number, since it uses less digits than its factorization.

21020825 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1193 (or 1188 counting only the distinct ones).

The product of its (nonzero) digits is 320, while the sum is 20.

The square root of 21020825 is about 4584.8473257024. The cubic root of 21020825 is about 275.9835852802.

Adding to 21020825 its reverse (52802012), we get a palindrome (73822837).

The spelling of 21020825 in words is "twenty-one million, twenty thousand, eight hundred twenty-five".