21138777 has 12 divisors (see below), whose sum is σ = 33309744. Its totient is φ = 12811320.

The previous prime is 21138751. The next prime is 21138781. The reversal of 21138777 is 77783112.

It is a happy number.

It is not a de Polignac number, because 21138777 - 2⁶ = 21138713 is a prime.

It is not an unprimeable number, because it can be changed into a prime (21138727) 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 11 ways as a sum of consecutive naturals, for example, 106663 + ... + 106860.

It is an arithmetic number, because the mean of its divisors is an integer number (2775812).

Almost surely, 2^21138777 is an apocalyptic number.

It is an amenable number.

21138777 is a deficient number, since it is larger than the sum of its proper divisors (12170967).

21138777 is a wasteful number, since it uses less digits than its factorization.

21138777 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 213540 (or 213537 counting only the distinct ones).

The product of its digits is 16464, while the sum is 36.

The square root of 21138777 is about 4597.6925734546. The cubic root of 21138777 is about 276.4988222446.

The spelling of 21138777 in words is "twenty-one million, one hundred thirty-eight thousand, seven hundred seventy-seven".