21821825 has 12 divisors (see below), whose sum is σ = 28236288. Its totient is φ = 16698000.

The previous prime is 21821819. The next prime is 21821843. The reversal of 21821825 is 52812812.

21821825 = T₁₃₆₆ + T₁₃₆₇ + ... + T₁₃₈₈.

It is a happy number.

It is not a de Polignac number, because 21821825 - 2¹⁶ = 21756289 is a prime.

It is a Duffinian number.

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, 18401 + ... + 19550.

It is an arithmetic number, because the mean of its divisors is an integer number (2353024).

Almost surely, 2^21821825 is an apocalyptic number.

21821825 is a gapful number since it is divisible by the number (25) formed by its first and last digit.

It is an amenable number.

21821825 is a deficient number, since it is larger than the sum of its proper divisors (6414463).

21821825 is a wasteful number, since it uses less digits than its factorization.

21821825 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 37984 (or 37979 counting only the distinct ones).

The product of its digits is 2560, while the sum is 29.

The square root of 21821825 is about 4671.3836280057. The cubic root of 21821825 is about 279.4454372324.

It can be divided in two parts, 2 and 1821825, that multiplied together give a triangular number (3643650 = T₂₆₉₉).

The spelling of 21821825 in words is "twenty-one million, eight hundred twenty-one thousand, eight hundred twenty-five".