21618471 has 16 divisors (see below), whose sum is σ = 33833984. Its totient is φ = 12019104.

The previous prime is 21618451. The next prime is 21618479. The reversal of 21618471 is 17481612.

It is not a de Polignac number, because 21618471 - 2¹¹ = 21616423 is a prime.

It is a super-3 number, since 3×21618471³ (a number of 23 digits) contains 333 as substring.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21618479) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 13135 + ... + 14688.

It is an arithmetic number, because the mean of its divisors is an integer number (2114624).

Almost surely, 2^21618471 is an apocalyptic number.

21618471 is a gapful number since it is divisible by the number (21) formed by its first and last digit.

21618471 is a deficient number, since it is larger than the sum of its proper divisors (12215513).

21618471 is a wasteful number, since it uses less digits than its factorization.

21618471 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 27870.

The product of its digits is 2688, while the sum is 30.

The square root of 21618471 is about 4649.5667540105. The cubic root of 21618471 is about 278.5746914617.

The spelling of 21618471 in words is "twenty-one million, six hundred eighteen thousand, four hundred seventy-one".