21481645 has 16 divisors (see below), whose sum is σ = 26812800. Its totient is φ = 16507584.

The previous prime is 21481643. The next prime is 21481651. The reversal of 21481645 is 54618412.

It is a cyclic number.

It is not a de Polignac number, because 21481645 - 2¹ = 21481643 is a prime.

It is a super-3 number, since 3×21481645³ (a number of 23 digits) contains 333 as substring. Note that it is a super-d number also for d = 2.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21481643) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 14656 + ... + 16054.

It is an arithmetic number, because the mean of its divisors is an integer number (1675800).

Almost surely, 2^21481645 is an apocalyptic number.

It is an amenable number.

21481645 is a deficient number, since it is larger than the sum of its proper divisors (5331155).

21481645 is a wasteful number, since it uses less digits than its factorization.

21481645 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1524.

The product of its digits is 7680, while the sum is 31.

The square root of 21481645 is about 4634.8295545791. The cubic root of 21481645 is about 277.9857358587.

The spelling of 21481645 in words is "twenty-one million, four hundred eighty-one thousand, six hundred forty-five".