21251471 has 4 divisors (see below), whose sum is σ = 22175472. Its totient is φ = 20327472.

The previous prime is 21251467. The next prime is 21251491. The reversal of 21251471 is 17415212.

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 21251471 - 2² = 21251467 is a prime.

It is a super-3 number, since 3×21251471³ (a number of 23 digits) contains 333 as substring.

It is a Harshad number since it is a multiple of its sum of digits (23), and also a Moran number because the ratio is a prime number: 923977 = 21251471 / (2 + 1 + 2 + 5 + 1 + 4 + 7 + 1).

It is a Duffinian number.

It is a plaindrome in base 16.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21251401) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 461966 + ... + 462011.

It is an arithmetic number, because the mean of its divisors is an integer number (5543868).

Almost surely, 2^21251471 is an apocalyptic number.

21251471 is a deficient number, since it is larger than the sum of its proper divisors (924001).

21251471 is an equidigital number, since it uses as much as digits as its factorization.

21251471 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 924000.

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

The square root of 21251471 is about 4609.9317782371. The cubic root of 21251471 is about 276.9893039352.

Adding to 21251471 its reverse (17415212), we get a palindrome (38666683).

The spelling of 21251471 in words is "twenty-one million, two hundred fifty-one thousand, four hundred seventy-one".