21025215 has 24 divisors (see below), whose sum is σ = 37222848. Its totient is φ = 10973760.

The previous prime is 21025211. The next prime is 21025217. The reversal of 21025215 is 51252012.

It is not a de Polignac number, because 21025215 - 2² = 21025211 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21025211) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 2856 + ... + 7085.

It is an arithmetic number, because the mean of its divisors is an integer number (1550952).

Almost surely, 2^21025215 is an apocalyptic number.

21025215 is a deficient number, since it is larger than the sum of its proper divisors (16197633).

21025215 is a wasteful number, since it uses less digits than its factorization.

21025215 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 9999 (or 9996 counting only the distinct ones).

The product of its (nonzero) digits is 200, while the sum is 18.

The square root of 21025215 is about 4585.3260516565. The cubic root of 21025215 is about 276.0027961279.

Adding to 21025215 its reverse (51252012), we get a palindrome (72277227).

It can be divided in two parts, 210 and 25215, that added together give a triangular number (25425 = T₂₂₅).

The spelling of 21025215 in words is "twenty-one million, twenty-five thousand, two hundred fifteen".