21777906 has 16 divisors (see below), whose sum is σ = 43639200. Its totient is φ = 7245408.

The previous prime is 21777893. The next prime is 21777907. The reversal of 21777906 is 60977712.

It is not an unprimeable number, because it can be changed into a prime (21777907) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 225 + ... + 6603.

It is an arithmetic number, because the mean of its divisors is an integer number (2727450).

Almost surely, 2^21777906 is an apocalyptic number.

21777906 is an abundant number, since it is smaller than the sum of its proper divisors (21861294).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

21777906 is a wasteful number, since it uses less digits than its factorization.

21777906 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 6953.

The product of its (nonzero) digits is 37044, while the sum is 39.

The square root of 21777906 is about 4666.6804047417. The cubic root of 21777906 is about 279.2578390064.

The spelling of 21777906 in words is "twenty-one million, seven hundred seventy-seven thousand, nine hundred six".