21570973 has 4 divisors (see below), whose sum is σ = 21600448. Its totient is φ = 21541500.

The previous prime is 21570929. The next prime is 21571001. The reversal of 21570973 is 37907512.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 21570973 - 2²¹ = 19473821 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21570173) 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, 13611 + ... + 15112.

It is an arithmetic number, because the mean of its divisors is an integer number (5400112).

Almost surely, 2^21570973 is an apocalyptic number.

It is an amenable number.

21570973 is a deficient number, since it is larger than the sum of its proper divisors (29475).

21570973 is an equidigital number, since it uses as much as digits as its factorization.

21570973 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 29474.

The product of its (nonzero) digits is 13230, while the sum is 34.

The square root of 21570973 is about 4644.4561576142. The cubic root of 21570973 is about 278.3705227975.

The spelling of 21570973 in words is "twenty-one million, five hundred seventy thousand, nine hundred seventy-three".