21745471 has 4 divisors (see below), whose sum is σ = 23722344. Its totient is φ = 19768600.

The previous prime is 21745469. The next prime is 21745483. The reversal of 21745471 is 17454712.

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 21745471 - 2¹ = 21745469 is a prime.

It is a super-3 number, since 3×21745471³ (a number of 23 digits) contains 333 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21745421) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 988420 + ... + 988441.

It is an arithmetic number, because the mean of its divisors is an integer number (5930586).

Almost surely, 2^21745471 is an apocalyptic number.

21745471 is a deficient number, since it is larger than the sum of its proper divisors (1976873).

21745471 is a wasteful number, since it uses less digits than its factorization.

21745471 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1976872.

The product of its digits is 7840, while the sum is 31.

The square root of 21745471 is about 4663.2039414977. The cubic root of 21745471 is about 279.1191322448.

The spelling of 21745471 in words is "twenty-one million, seven hundred forty-five thousand, four hundred seventy-one".