21072071 has 4 divisors (see below), whose sum is σ = 21988272. Its totient is φ = 20155872.

The previous prime is 21072053. The next prime is 21072101. The reversal of 21072071 is 17027012.

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

It is a cyclic number.

It is not a de Polignac number, because 21072071 - 2¹⁴ = 21055687 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 (21072011) 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, 458066 + ... + 458111.

It is an arithmetic number, because the mean of its divisors is an integer number (5497068).

Almost surely, 2^21072071 is an apocalyptic number.

21072071 is a deficient number, since it is larger than the sum of its proper divisors (916201).

21072071 is an equidigital number, since it uses as much as digits as its factorization.

21072071 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 916200.

The product of its (nonzero) digits is 196, while the sum is 20.

The square root of 21072071 is about 4590.4325504249. The cubic root of 21072071 is about 276.2076738112.

Adding to 21072071 its reverse (17027012), we get a palindrome (38099083).

The spelling of 21072071 in words is "twenty-one million, seventy-two thousand, seventy-one".