21829871 has 4 divisors (see below), whose sum is σ = 24948432. Its totient is φ = 18711312.

The previous prime is 21829861. The next prime is 21829897. The reversal of 21829871 is 17892812.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 21829871 - 2¹⁰ = 21828847 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21829861) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 1559270 + ... + 1559283.

It is an arithmetic number, because the mean of its divisors is an integer number (6237108).

Almost surely, 2^21829871 is an apocalyptic number.

21829871 is a deficient number, since it is larger than the sum of its proper divisors (3118561).

21829871 is an equidigital number, since it uses as much as digits as its factorization.

21829871 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3118560.

The product of its digits is 16128, while the sum is 38.

The square root of 21829871 is about 4672.2447495824. The cubic root of 21829871 is about 279.4797781076.

The spelling of 21829871 in words is "twenty-one million, eight hundred twenty-nine thousand, eight hundred seventy-one".