21777957 has 16 divisors (see below), whose sum is σ = 32417280. Its totient is φ = 14449536.

The previous prime is 21777953. The next prime is 21777979. The reversal of 21777957 is 75977712.

It is not a de Polignac number, because 21777957 - 2² = 21777953 is a prime.

It is a super-2 number, since 2×21777957² = 948558822187698, which contains 22 as substring.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21777953) 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 15 ways as a sum of consecutive naturals, for example, 4213 + ... + 7829.

It is an arithmetic number, because the mean of its divisors is an integer number (2026080).

Almost surely, 2^21777957 is an apocalyptic number.

21777957 is a gapful number since it is divisible by the number (27) formed by its first and last digit.

It is an amenable number.

21777957 is a deficient number, since it is larger than the sum of its proper divisors (10639323).

21777957 is a wasteful number, since it uses less digits than its factorization.

21777957 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3849 (or 3843 counting only the distinct ones).

The product of its digits is 216090, while the sum is 45.

The square root of 21777957 is about 4666.6858690081. The cubic root of 21777957 is about 279.2580569971.

The spelling of 21777957 in words is "twenty-one million, seven hundred seventy-seven thousand, nine hundred fifty-seven".