21081706 has 8 divisors (see below), whose sum is σ = 31657860. Its totient is φ = 10529088.

The previous prime is 21081691. The next prime is 21081707. The reversal of 21081706 is 60718012.

It can be written as a sum of positive squares in 2 ways, for example, as 19882681 + 1199025 = 4459^2 + 1095^2 .

It is a sphenic number, since it is the product of 3 distinct primes.

It is not an unprimeable number, because it can be changed into a prime (21081707) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 3441 + ... + 7348.

Almost surely, 2^21081706 is an apocalyptic number.

21081706 is a deficient number, since it is larger than the sum of its proper divisors (10576154).

21081706 is a wasteful number, since it uses less digits than its factorization.

21081706 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 11768.

The product of its (nonzero) digits is 672, while the sum is 25.

The square root of 21081706 is about 4591.4818958589. The cubic root of 21081706 is about 276.2497651561.

Adding to 21081706 its reverse (60718012), we get a palindrome (81799718).

The spelling of 21081706 in words is "twenty-one million, eighty-one thousand, seven hundred six".