21278025 has 48 divisors (see below), whose sum is σ = 40473600. Its totient is φ = 10946880.

The previous prime is 21278021. The next prime is 21278041. The reversal of 21278025 is 52087212.

It is not a de Polignac number, because 21278025 - 2² = 21278021 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (27).

It is a self number, because there is not a number n which added to its sum of digits gives 21278025.

It is not an unprimeable number, because it can be changed into a prime (21278021) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 47 ways as a sum of consecutive naturals, for example, 19032 + ... + 20118.

It is an arithmetic number, because the mean of its divisors is an integer number (843200).

Almost surely, 2^21278025 is an apocalyptic number.

21278025 is a gapful number since it is divisible by the number (25) formed by its first and last digit.

It is an amenable number.

21278025 is a deficient number, since it is larger than the sum of its proper divisors (19195575).

21278025 is a wasteful number, since it uses less digits than its factorization.

21278025 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1135 (or 1124 counting only the distinct ones).

The product of its (nonzero) digits is 2240, while the sum is 27.

The square root of 21278025 is about 4612.8109651274. The cubic root of 21278025 is about 277.1046232095.

The spelling of 21278025 in words is "twenty-one million, two hundred seventy-eight thousand, twenty-five".