21403289 has 4 divisors (see below), whose sum is σ = 22662324. Its totient is φ = 20144256.

The previous prime is 21403273. The next prime is 21403303. The reversal of 21403289 is 98230412.

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 12355225 + 9048064 = 3515^2 + 3008^2 .

It is a cyclic number.

It is not a de Polignac number, because 21403289 - 2⁴ = 21403273 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21403229) 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, 629492 + ... + 629525.

It is an arithmetic number, because the mean of its divisors is an integer number (5665581).

Almost surely, 2^21403289 is an apocalyptic number.

It is an amenable number.

21403289 is a deficient number, since it is larger than the sum of its proper divisors (1259035).

21403289 is a wasteful number, since it uses less digits than its factorization.

21403289 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1259034.

The product of its (nonzero) digits is 3456, while the sum is 29.

The square root of 21403289 is about 4626.3688785050. The cubic root of 21403289 is about 277.6473324172.

The spelling of 21403289 in words is "twenty-one million, four hundred three thousand, two hundred eighty-nine".