21615441 has 16 divisors (see below), whose sum is σ = 29804544. Its totient is φ = 13926224.

The previous prime is 21615413. The next prime is 21615457. The reversal of 21615441 is 14451612.

It is a happy number.

It is a cyclic number.

It is not a de Polignac number, because 21615441 - 2⁵ = 21615409 is a prime.

It is a super-3 number, since 3×21615441³ (a number of 23 digits) contains 333 as substring.

It is not an unprimeable number, because it can be changed into a prime (21615481) 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, 10780 + ... + 12626.

It is an arithmetic number, because the mean of its divisors is an integer number (1862784).

Almost surely, 2^21615441 is an apocalyptic number.

It is an amenable number.

21615441 is a deficient number, since it is larger than the sum of its proper divisors (8189103).

21615441 is a wasteful number, since it uses less digits than its factorization.

21615441 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1980.

The product of its digits is 960, while the sum is 24.

The square root of 21615441 is about 4649.2409057824. The cubic root of 21615441 is about 278.5616760369.

The spelling of 21615441 in words is "twenty-one million, six hundred fifteen thousand, four hundred forty-one".