21570919 has 4 divisors (see below), whose sum is σ = 21580344. Its totient is φ = 21561496.

The previous prime is 21570917. The next prime is 21570929. The reversal of 21570919 is 91907512.

It is a semiprime because it is the product of two primes, and also a brilliant number, because the two primes have the same length.

It is a cyclic number.

It is not a de Polignac number, because 21570919 - 2¹ = 21570917 is a prime.

It is a super-2 number, since 2×21570919² = 930609093009122, which contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21570917) 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, 1164 + ... + 6670.

It is an arithmetic number, because the mean of its divisors is an integer number (5395086).

Almost surely, 2^21570919 is an apocalyptic number.

21570919 is a deficient number, since it is larger than the sum of its proper divisors (9425).

21570919 is an equidigital number, since it uses as much as digits as its factorization.

21570919 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 9424.

The product of its (nonzero) digits is 5670, while the sum is 34.

The square root of 21570919 is about 4644.4503442280. The cubic root of 21570919 is about 278.3702905097.

The spelling of 21570919 in words is "twenty-one million, five hundred seventy thousand, nine hundred nineteen".