21687307 has 2 divisors, whose sum is σ = 21687308. Its totient is φ = 21687306.

The previous prime is 21687301. The next prime is 21687329. The reversal of 21687307 is 70378612.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 21687307 - 2²³ = 13298699 is a prime.

It is not a weakly prime, because it can be changed into another prime (21687301) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10843653 + 10843654.

It is an arithmetic number, because the mean of its divisors is an integer number (10843654).

Almost surely, 2^21687307 is an apocalyptic number.

21687307 is a deficient number, since it is larger than the sum of its proper divisors (1).

21687307 is an equidigital number, since it uses as much as digits as its factorization.

21687307 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 14112, while the sum is 34.

The square root of 21687307 is about 4656.9632809375. The cubic root of 21687307 is about 278.8700507785.

The spelling of 21687307 in words is "twenty-one million, six hundred eighty-seven thousand, three hundred seven".