21245899 has 4 divisors (see below), whose sum is σ = 21255760. Its totient is φ = 21236040.

The previous prime is 21245867. The next prime is 21245911. The reversal of 21245899 is 99854212.

21245899 = T₃₇₆₂ + T₃₇₆₃ + T₃₇₆₄.

It is a semiprime because it is the product of two primes, and also a brilliant number, because the two primes have the same length.

It is a cyclic number.

It is not a de Polignac number, because 21245899 - 2⁵ = 21245867 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21245839) 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 3 ways as a sum of consecutive naturals, for example, 159 + ... + 6520.

It is an arithmetic number, because the mean of its divisors is an integer number (5313940).

Almost surely, 2^21245899 is an apocalyptic number.

21245899 is the 3764-th centered triangular number.

21245899 is a deficient number, since it is larger than the sum of its proper divisors (9861).

21245899 is an equidigital number, since it uses as much as digits as its factorization.

21245899 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 9860.

The product of its digits is 51840, while the sum is 40.

The square root of 21245899 is about 4609.3273912796. The cubic root of 21245899 is about 276.9650935435.

The spelling of 21245899 in words is "twenty-one million, two hundred forty-five thousand, eight hundred ninety-nine".