21400873 has 4 divisors (see below), whose sum is σ = 23047108. Its totient is φ = 19754640.

The previous prime is 21400849. The next prime is 21400877. The reversal of 21400873 is 37800412.

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

It can be written as a sum of positive squares in 2 ways, for example, as 2111209 + 19289664 = 1453^2 + 4392^2 .

It is a cyclic number.

It is not a de Polignac number, because 21400873 - 2⁹ = 21400361 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21400877) 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 3 ways as a sum of consecutive naturals, for example, 823098 + ... + 823123.

It is an arithmetic number, because the mean of its divisors is an integer number (5761777).

Almost surely, 2^21400873 is an apocalyptic number.

It is an amenable number.

21400873 is a deficient number, since it is larger than the sum of its proper divisors (1646235).

21400873 is a wasteful number, since it uses less digits than its factorization.

21400873 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1646234.

The product of its (nonzero) digits is 1344, while the sum is 25.

The square root of 21400873 is about 4626.1077592291. The cubic root of 21400873 is about 277.6368850946.

The spelling of 21400873 in words is "twenty-one million, four hundred thousand, eight hundred seventy-three".