21211457 has 4 divisors (see below), whose sum is σ = 21290580. Its totient is φ = 21132336.

The previous prime is 21211433. The next prime is 21211481. The reversal of 21211457 is 75411212.

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

It is an interprime number because it is at equal distance from previous prime (21211433) and next prime (21211481).

It can be written as a sum of positive squares in 2 ways, for example, as 1132096 + 20079361 = 1064^2 + 4481^2 .

It is a cyclic number.

It is not a de Polignac number, because 21211457 - 2¹⁰ = 21210433 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21216457) 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, 39158 + ... + 39695.

It is an arithmetic number, because the mean of its divisors is an integer number (5322645).

Almost surely, 2^21211457 is an apocalyptic number.

It is an amenable number.

21211457 is a deficient number, since it is larger than the sum of its proper divisors (79123).

21211457 is an equidigital number, since it uses as much as digits as its factorization.

21211457 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 79122.

The product of its digits is 560, while the sum is 23.

The square root of 21211457 is about 4605.5897559379. The cubic root of 21211457 is about 276.8153487053.

Adding to 21211457 its reverse (75411212), we get a palindrome (96622669).

The spelling of 21211457 in words is "twenty-one million, two hundred eleven thousand, four hundred fifty-seven".