21013787 has 2 divisors, whose sum is σ = 21013788. Its totient is φ = 21013786.

The previous prime is 21013781. The next prime is 21013823. The reversal of 21013787 is 78731012.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 21013787 - 2⁶ = 21013723 is a prime.

It is not a weakly prime, because it can be changed into another prime (21013781) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10506893 + 10506894.

It is an arithmetic number, because the mean of its divisors is an integer number (10506894).

Almost surely, 2^21013787 is an apocalyptic number.

21013787 is a deficient number, since it is larger than the sum of its proper divisors (1).

21013787 is an equidigital number, since it uses as much as digits as its factorization.

21013787 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 2352, while the sum is 29.

The square root of 21013787 is about 4584.0797331635. The cubic root of 21013787 is about 275.9527810770.

Adding to 21013787 its reverse (78731012), we get a palindrome (99744799).

The spelling of 21013787 in words is "twenty-one million, thirteen thousand, seven hundred eighty-seven".