21000025 has 12 divisors (see below), whose sum is σ = 26409024. Its totient is φ = 16562000.

The previous prime is 20999999. The next prime is 21000037. The reversal of 21000025 is 52000012.

It is not a de Polignac number, because 21000025 - 2⁹ = 20999513 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 20999975 and 21000020.

It is an unprimeable number.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 4141 + ... + 7690.

It is an arithmetic number, because the mean of its divisors is an integer number (2200752).

Almost surely, 2^21000025 is an apocalyptic number.

21000025 is a gapful number since it is divisible by the number (25) formed by its first and last digit.

It is an amenable number.

21000025 is a deficient number, since it is larger than the sum of its proper divisors (5408999).

21000025 is a wasteful number, since it uses less digits than its factorization.

21000025 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 11912 (or 11907 counting only the distinct ones).

The product of its (nonzero) digits is 20, while the sum is 10.

The square root of 21000025 is about 4582.5784226787. The cubic root of 21000025 is about 275.8925271192.

Adding to 21000025 its reverse (52000012), we get a palindrome (73000037).

The spelling of 21000025 in words is "twenty-one million, twenty-five", and thus it is an aban number and an uban number.