21682705 has 16 divisors (see below), whose sum is σ = 29880000. Its totient is φ = 14938560.

The previous prime is 21682699. The next prime is 21682709. The reversal of 21682705 is 50728612.

It is not a de Polignac number, because 21682705 - 2³ = 21682697 is a prime.

It is a super-2 number, since 2×21682705² = 940279392234050, which contains 22 as substring.

It is not an unprimeable number, because it can be changed into a prime (21682709) 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, 9330 + ... + 11419.

It is an arithmetic number, because the mean of its divisors is an integer number (1867500).

Almost surely, 2^21682705 is an apocalyptic number.

It is an amenable number.

21682705 is a deficient number, since it is larger than the sum of its proper divisors (8197295).

21682705 is a wasteful number, since it uses less digits than its factorization.

21682705 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 20784.

The product of its (nonzero) digits is 6720, while the sum is 31.

The square root of 21682705 is about 4656.4691559163. The cubic root of 21682705 is about 278.8503241743.

The spelling of 21682705 in words is "twenty-one million, six hundred eighty-two thousand, seven hundred five".