21409873 has 4 divisors (see below), whose sum is σ = 21479920. Its totient is φ = 21339828.

The previous prime is 21409867. The next prime is 21409907. The reversal of 21409873 is 37890412.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 21409873 - 2⁹ = 21409361 is a prime.

It is a super-2 number, since 2×21409873² = 916765323752258, which contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21409823) 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, 34563 + ... + 35176.

It is an arithmetic number, because the mean of its divisors is an integer number (5369980).

Almost surely, 2^21409873 is an apocalyptic number.

It is an amenable number.

21409873 is a deficient number, since it is larger than the sum of its proper divisors (70047).

21409873 is an equidigital number, since it uses as much as digits as its factorization.

21409873 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 70046.

The product of its (nonzero) digits is 12096, while the sum is 34.

The square root of 21409873 is about 4627.0803969674. The cubic root of 21409873 is about 277.6757991110.

The spelling of 21409873 in words is "twenty-one million, four hundred nine thousand, eight hundred seventy-three".