21250687 has 2 divisors, whose sum is σ = 21250688. Its totient is φ = 21250686.

The previous prime is 21250637. The next prime is 21250693. The reversal of 21250687 is 78605212.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 21250687 - 2¹¹ = 21248639 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21250637) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10625343 + 10625344.

It is an arithmetic number, because the mean of its divisors is an integer number (10625344).

Almost surely, 2^21250687 is an apocalyptic number.

21250687 is a deficient number, since it is larger than the sum of its proper divisors (1).

21250687 is an equidigital number, since it uses as much as digits as its factorization.

21250687 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 6720, while the sum is 31.

The square root of 21250687 is about 4609.8467436565. The cubic root of 21250687 is about 276.9858977038.

Adding to 21250687 its reverse (78605212), we get a palindrome (99855899).

The spelling of 21250687 in words is "twenty-one million, two hundred fifty thousand, six hundred eighty-seven".