21188747 has 2 divisors, whose sum is σ = 21188748. Its totient is φ = 21188746.

The previous prime is 21188737. The next prime is 21188789. The reversal of 21188747 is 74788112.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 21188747 - 2⁴ = 21188731 is a prime.

It is a Chen prime.

It is a self number, because there is not a number n which added to its sum of digits gives 21188747.

It is not a weakly prime, because it can be changed into another prime (21188707) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10594373 + 10594374.

It is an arithmetic number, because the mean of its divisors is an integer number (10594374).

Almost surely, 2^21188747 is an apocalyptic number.

21188747 is a deficient number, since it is larger than the sum of its proper divisors (1).

21188747 is an equidigital number, since it uses as much as digits as its factorization.

21188747 is an evil number, because the sum of its binary digits is even.

The product of its digits is 25088, while the sum is 38.

The square root of 21188747 is about 4603.1236133739. The cubic root of 21188747 is about 276.7165228454.

The spelling of 21188747 in words is "twenty-one million, one hundred eighty-eight thousand, seven hundred forty-seven".