21257371 has 4 divisors (see below), whose sum is σ = 22376200. Its totient is φ = 20138544.

The previous prime is 21257347. The next prime is 21257407. The reversal of 21257371 is 17375212.

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 21257371 - 2¹¹ = 21255323 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21257671) 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, 559386 + ... + 559423.

It is an arithmetic number, because the mean of its divisors is an integer number (5594050).

Almost surely, 2^21257371 is an apocalyptic number.

21257371 is a deficient number, since it is larger than the sum of its proper divisors (1118829).

21257371 is a wasteful number, since it uses less digits than its factorization.

21257371 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1118828.

The product of its digits is 2940, while the sum is 28.

The square root of 21257371 is about 4610.5716565302. The cubic root of 21257371 is about 277.0149348775.

The spelling of 21257371 in words is "twenty-one million, two hundred fifty-seven thousand, three hundred seventy-one".