21864977 has 4 divisors (see below), whose sum is σ = 21894180. Its totient is φ = 21835776.

The previous prime is 21864959. The next prime is 21864989. The reversal of 21864977 is 77946812.

It is a Cunningham number, because it is equal to 4676²+1.

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 8549776 + 13315201 = 2924^2 + 3649^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21864977 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21864377) 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, 13448 + ... + 14985.

It is an arithmetic number, because the mean of its divisors is an integer number (5473545).

Almost surely, 2^21864977 is an apocalyptic number.

It is an amenable number.

21864977 is a deficient number, since it is larger than the sum of its proper divisors (29203).

21864977 is an equidigital number, since it uses as much as digits as its factorization.

21864977 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 29202.

The product of its digits is 169344, while the sum is 44.

The square root of 21864977 is about 4676.0001069290. Note that the first 3 decimals coincide. The cubic root of 21864977 is about 279.6295142547.

The spelling of 21864977 in words is "twenty-one million, eight hundred sixty-four thousand, nine hundred seventy-seven".