21681413 has 16 divisors (see below), whose sum is σ = 24998400. Its totient is φ = 18636480.

The previous prime is 21681389. The next prime is 21681421. The reversal of 21681413 is 31418612.

It is a cyclic number.

It is not a de Polignac number, because 21681413 - 2¹² = 21677317 is a prime.

It is a Duffinian number.

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21681113) 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 15 ways as a sum of consecutive naturals, for example, 14348 + ... + 15786.

It is an arithmetic number, because the mean of its divisors is an integer number (1562400).

Almost surely, 2^21681413 is an apocalyptic number.

It is an amenable number.

21681413 is a deficient number, since it is larger than the sum of its proper divisors (3316987).

21681413 is a wasteful number, since it uses less digits than its factorization.

21681413 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1532.

The product of its digits is 1152, while the sum is 26.

The square root of 21681413 is about 4656.3304221243. The cubic root of 21681413 is about 278.8447854777.

The spelling of 21681413 in words is "twenty-one million, six hundred eighty-one thousand, four hundred thirteen".