21007707 has 8 divisors (see below), whose sum is σ = 32011776. Its totient is φ = 12004392.

The previous prime is 21007691. The next prime is 21007709. The reversal of 21007707 is 70770012.

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

It is not a de Polignac number, because 21007707 - 2⁴ = 21007691 is a prime.

It is not an unprimeable number, because it can be changed into a prime (21007709) 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, 500163 + ... + 500204.

It is an arithmetic number, because the mean of its divisors is an integer number (4001472).

Almost surely, 2^21007707 is an apocalyptic number.

21007707 is a deficient number, since it is larger than the sum of its proper divisors (11004069).

21007707 is a wasteful number, since it uses less digits than its factorization.

21007707 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1000377.

The product of its (nonzero) digits is 686, while the sum is 24.

The square root of 21007707 is about 4583.4165204572. The cubic root of 21007707 is about 275.9261643492.

Adding to 21007707 its reverse (70770012), we get a palindrome (91777719).

The spelling of 21007707 in words is "twenty-one million, seven thousand, seven hundred seven".