21006777 has 8 divisors (see below), whose sum is σ = 30555360. Its totient is φ = 12731360.

The previous prime is 21006743. The next prime is 21006779. The reversal of 21006777 is 77760012.

It is a happy number.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 21006777 - 2¹⁰ = 21005753 is a prime.

It is not an unprimeable number, because it can be changed into a prime (21006779) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 318252 + ... + 318317.

It is an arithmetic number, because the mean of its divisors is an integer number (3819420).

Almost surely, 2^21006777 is an apocalyptic number.

It is an amenable number.

21006777 is a deficient number, since it is larger than the sum of its proper divisors (9548583).

21006777 is a wasteful number, since it uses less digits than its factorization.

21006777 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 636583.

The product of its (nonzero) digits is 4116, while the sum is 30.

The square root of 21006777 is about 4583.3150666303. The cubic root of 21006777 is about 275.9220925877.

Adding to 21006777 its reverse (77760012), we get a palindrome (98766789).

The spelling of 21006777 in words is "twenty-one million, six thousand, seven hundred seventy-seven".