21999825 has 18 divisors (see below), whose sum is σ = 39404534. Its totient is φ = 11733120.

The previous prime is 21999811. The next prime is 21999839. The reversal of 21999825 is 52899912.

It is an interprime number because it is at equal distance from previous prime (21999811) and next prime (21999839).

It can be written as a sum of positive squares in 3 ways, for example, as 321489 + 21678336 = 567^2 + 4656^2 .

It is not a de Polignac number, because 21999825 - 2¹¹ = 21997777 is a prime.

It is a hoax number, since the sum of its digits (45) coincides with the sum of the digits of its distinct prime factors.

It is a Harshad number since it is a multiple of its sum of digits (45).

It is a Duffinian number.

It is a Curzon number.

It is an unprimeable number.

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 17 ways as a sum of consecutive naturals, for example, 48664 + ... + 49113.

Almost surely, 2^21999825 is an apocalyptic number.

21999825 is a gapful number since it is divisible by the number (25) formed by its first and last digit.

It is an amenable number.

21999825 is a deficient number, since it is larger than the sum of its proper divisors (17404709).

21999825 is a wasteful number, since it uses less digits than its factorization.

21999825 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 97793 (or 97785 counting only the distinct ones).

The product of its digits is 116640, while the sum is 45.

The square root of 21999825 is about 4690.3971047237. The cubic root of 21999825 is about 280.2031900986.

The spelling of 21999825 in words is "twenty-one million, nine hundred ninety-nine thousand, eight hundred twenty-five".