21663877 has 4 divisors (see below), whose sum is σ = 21698316. Its totient is φ = 21629440.

The previous prime is 21663871. The next prime is 21663881. The reversal of 21663877 is 77836612.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 14699556 + 6964321 = 3834^2 + 2639^2 .

It is a cyclic number.

It is not a de Polignac number, because 21663877 - 2³ = 21663869 is a prime.

It is a super-2 number, since 2×21663877² = 938647133342258, which contains 22 as substring.

It is a Smith number, since the sum of its digits (40) coincides with the sum of the digits of its prime factors. Since it is squarefree, it is also a hoax number.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21663871) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 16258 + ... + 17539.

It is an arithmetic number, because the mean of its divisors is an integer number (5424579).

Almost surely, 2^21663877 is an apocalyptic number.

It is an amenable number.

21663877 is a deficient number, since it is larger than the sum of its proper divisors (34439).

21663877 is an equidigital number, since it uses as much as digits as its factorization.

21663877 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 34438.

The product of its digits is 84672, while the sum is 40.

The square root of 21663877 is about 4654.4470133411. The cubic root of 21663877 is about 278.7695883330.

The spelling of 21663877 in words is "twenty-one million, six hundred sixty-three thousand, eight hundred seventy-seven".