21281707 has 2 divisors, whose sum is σ = 21281708. Its totient is φ = 21281706.

The previous prime is 21281683. The next prime is 21281719. The reversal of 21281707 is 70718212.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 21281707 - 2²³ = 12893099 is a prime.

It is a super-2 number, since 2×21281707² = 905822105667698, which contains 22 as substring.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (21281797) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10640853 + 10640854.

It is an arithmetic number, because the mean of its divisors is an integer number (10640854).

Almost surely, 2^21281707 is an apocalyptic number.

21281707 is a deficient number, since it is larger than the sum of its proper divisors (1).

21281707 is an equidigital number, since it uses as much as digits as its factorization.

21281707 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 1568, while the sum is 28.

The square root of 21281707 is about 4613.2100537478. The cubic root of 21281707 is about 277.1206059017.

Adding to 21281707 its reverse (70718212), we get a palindrome (91999919).

The spelling of 21281707 in words is "twenty-one million, two hundred eighty-one thousand, seven hundred seven".