21370609 has 4 divisors (see below), whose sum is σ = 23014516. Its totient is φ = 19726704.

The previous prime is 21370603. The next prime is 21370619. The reversal of 21370609 is 90607312.

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 13162384 + 8208225 = 3628^2 + 2865^2 .

It is a cyclic number.

It is not a de Polignac number, because 21370609 - 2¹³ = 21362417 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21370603) 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, 821934 + ... + 821959.

It is an arithmetic number, because the mean of its divisors is an integer number (5753629).

Almost surely, 2^21370609 is an apocalyptic number.

It is an amenable number.

21370609 is a deficient number, since it is larger than the sum of its proper divisors (1643907).

21370609 is a wasteful number, since it uses less digits than its factorization.

21370609 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1643906.

The product of its (nonzero) digits is 2268, while the sum is 28.

The square root of 21370609 is about 4622.8356016627. The cubic root of 21370609 is about 277.5059501470.

The spelling of 21370609 in words is "twenty-one million, three hundred seventy thousand, six hundred nine".