21570023 has 4 divisors (see below), whose sum is σ = 21771720. Its totient is φ = 21368328.

The previous prime is 21570019. The next prime is 21570041. The reversal of 21570023 is 32007512.

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

It is not a de Polignac number, because 21570023 - 2² = 21570019 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 21569977 and 21570004.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21570053) 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, 100688 + ... + 100901.

It is an arithmetic number, because the mean of its divisors is an integer number (5442930).

Almost surely, 2^21570023 is an apocalyptic number.

21570023 is a deficient number, since it is larger than the sum of its proper divisors (201697).

21570023 is a wasteful number, since it uses less digits than its factorization.

21570023 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 201696.

The product of its (nonzero) digits is 420, while the sum is 20.

The square root of 21570023 is about 4644.3538840187. The cubic root of 21570023 is about 278.3664361965.

Adding to 21570023 its reverse (32007512), we get a palindrome (53577535).

The spelling of 21570023 in words is "twenty-one million, five hundred seventy thousand, twenty-three".