21857829 has 16 divisors (see below), whose sum is σ = 33485952. Its totient is φ = 12423168.

The previous prime is 21857827. The next prime is 21857831. The reversal of 21857829 is 92875812.

It is an interprime number because it is at equal distance from previous prime (21857827) and next prime (21857831).

It is not a de Polignac number, because 21857829 - 2¹ = 21857827 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21857827) 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 15 ways as a sum of consecutive naturals, for example, 1357 + ... + 6749.

It is an arithmetic number, because the mean of its divisors is an integer number (2092872).

Almost surely, 2^21857829 is an apocalyptic number.

It is an amenable number.

21857829 is a deficient number, since it is larger than the sum of its proper divisors (11628123).

21857829 is a wasteful number, since it uses less digits than its factorization.

21857829 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 5596.

The product of its digits is 80640, while the sum is 42.

The square root of 21857829 is about 4675.2357159827. The cubic root of 21857829 is about 279.5990391923.

The spelling of 21857829 in words is "twenty-one million, eight hundred fifty-seven thousand, eight hundred twenty-nine".