21025810 has 32 divisors (see below), whose sum is σ = 41014512. Its totient is φ = 7714560.

The previous prime is 21025793. The next prime is 21025811. The reversal of 21025810 is 1852012.

It can be written as a sum of positive squares in 8 ways, for example, as 9199089 + 11826721 = 3033^2 + 3439^2 .

It is a super-2 number, since 2×21025810² = 884169372312200, which contains 22 as substring.

It is not an unprimeable number, because it can be changed into a prime (21025811) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 25200 + ... + 26020.

Almost surely, 2^21025810 is an apocalyptic number.

21025810 is a deficient number, since it is larger than the sum of its proper divisors (19988702).

21025810 is a wasteful number, since it uses less digits than its factorization.

21025810 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1038.

The product of its (nonzero) digits is 160, while the sum is 19.

The square root of 21025810 is about 4585.3909320798. The cubic root of 21025810 is about 276.0053996703.

Adding to 21025810 its reverse (1852012), we get a palindrome (22877822).

The spelling of 21025810 in words is "twenty-one million, twenty-five thousand, eight hundred ten".