21457777 has 6 divisors (see below), whose sum is σ = 23585954. Its totient is φ = 19506960.

The previous prime is 21457771. The next prime is 21457819. The reversal of 21457777 is 77775412.

It can be written as a sum of positive squares in only one way, i.e., 12702096 + 8755681 = 3564^2 + 2959^2 .

It is not a de Polignac number, because 21457777 - 2⁷ = 21457649 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21457771) by changing a digit.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 88548 + ... + 88789.

Almost surely, 2^21457777 is an apocalyptic number.

It is an amenable number.

21457777 is a deficient number, since it is larger than the sum of its proper divisors (2128177).

21457777 is a wasteful number, since it uses less digits than its factorization.

21457777 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 177359 (or 177348 counting only the distinct ones).

The product of its digits is 96040, while the sum is 40.

The square root of 21457777 is about 4632.2539869916. The cubic root of 21457777 is about 277.8827421571.

The spelling of 21457777 in words is "twenty-one million, four hundred fifty-seven thousand, seven hundred seventy-seven".