21011787 has 6 divisors (see below), whose sum is σ = 30350372. Its totient is φ = 14007852.

The previous prime is 21011761. The next prime is 21011789. The reversal of 21011787 is 78711012.

It is not a de Polignac number, because 21011787 - 2⁷ = 21011659 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 21011787.

It is not an unprimeable number, because it can be changed into a prime (21011789) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 1167313 + ... + 1167330.

Almost surely, 2^21011787 is an apocalyptic number.

21011787 is a deficient number, since it is larger than the sum of its proper divisors (9338585).

21011787 is a wasteful number, since it uses less digits than its factorization.

21011787 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2334649 (or 2334646 counting only the distinct ones).

The product of its (nonzero) digits is 784, while the sum is 27.

The square root of 21011787 is about 4583.8615816798. The cubic root of 21011787 is about 275.9440261412.

Adding to 21011787 its reverse (78711012), we get a palindrome (99722799).

The spelling of 21011787 in words is "twenty-one million, eleven thousand, seven hundred eighty-seven".