21251707 has 4 divisors (see below), whose sum is σ = 21283776. Its totient is φ = 21219640.

The previous prime is 21251689. The next prime is 21251719. The reversal of 21251707 is 70715212.

It is a happy number.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 21251707 - 2²³ = 12863099 is a prime.

It is a Duffinian number.

It is a plaindrome in base 16.

It is not an unprimeable number, because it can be changed into a prime (21254707) 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, 15019 + ... + 16372.

It is an arithmetic number, because the mean of its divisors is an integer number (5320944).

Almost surely, 2^21251707 is an apocalyptic number.

21251707 is a deficient number, since it is larger than the sum of its proper divisors (32069).

21251707 is an equidigital number, since it uses as much as digits as its factorization.

21251707 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 32068.

The product of its (nonzero) digits is 980, while the sum is 25.

The square root of 21251707 is about 4609.9573750741. The cubic root of 21251707 is about 276.9903292640.

Adding to 21251707 its reverse (70715212), we get a palindrome (91966919).

The spelling of 21251707 in words is "twenty-one million, two hundred fifty-one thousand, seven hundred seven".