21409871 has 8 divisors (see below), whose sum is σ = 25257984. Its totient is φ = 17759160.

The previous prime is 21409867. The next prime is 21409907. The reversal of 21409871 is 17890412.

21409871 = 816² + 817² + ... + 846².

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 21409871 - 2² = 21409867 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 (21409471) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 49115 + ... + 49548.

It is an arithmetic number, because the mean of its divisors is an integer number (3157248).

Almost surely, 2^21409871 is an apocalyptic number.

21409871 is a deficient number, since it is larger than the sum of its proper divisors (3848113).

21409871 is an equidigital number, since it uses as much as digits as its factorization.

21409871 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 98701.

The product of its (nonzero) digits is 4032, while the sum is 32.

The square root of 21409871 is about 4627.0801808484. The cubic root of 21409871 is about 277.6757904647.

The spelling of 21409871 in words is "twenty-one million, four hundred nine thousand, eight hundred seventy-one".