21051706 has 16 divisors (see below), whose sum is σ = 34650504. Its totient is φ = 9532224.

The previous prime is 21051703. The next prime is 21051707. The reversal of 21051706 is 60715012.

It can be written as a sum of positive squares in 4 ways, for example, as 11840481 + 9211225 = 3441^2 + 3035^2 .

It is not an unprimeable number, because it can be changed into a prime (21051703) 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 7 ways as a sum of consecutive naturals, for example, 6261 + ... + 9016.

Almost surely, 2^21051706 is an apocalyptic number.

21051706 is a gapful number since it is divisible by the number (26) formed by its first and last digit.

21051706 is a deficient number, since it is larger than the sum of its proper divisors (13598798).

21051706 is a wasteful number, since it uses less digits than its factorization.

21051706 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 15345.

The product of its (nonzero) digits is 420, while the sum is 22.

The square root of 21051706 is about 4588.2138136752. The cubic root of 21051706 is about 276.1186652790.

Adding to 21051706 its reverse (60715012), we get a palindrome (81766718).

The spelling of 21051706 in words is "twenty-one million, fifty-one thousand, seven hundred six".