21647977 has 8 divisors (see below), whose sum is σ = 23595264. Its totient is φ = 19741008.

The previous prime is 21647957. The next prime is 21647993. The reversal of 21647977 is 77974612.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 21647977 - 2¹⁹ = 21123689 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21647917) 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 7 ways as a sum of consecutive naturals, for example, 8953 + ... + 11110.

It is an arithmetic number, because the mean of its divisors is an integer number (2949408).

Almost surely, 2^21647977 is an apocalyptic number.

It is an amenable number.

21647977 is a deficient number, since it is larger than the sum of its proper divisors (1947287).

21647977 is a wasteful number, since it uses less digits than its factorization.

21647977 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 20159.

The product of its digits is 148176, while the sum is 43.

The square root of 21647977 is about 4652.7386558886. The cubic root of 21647977 is about 278.7013715302.

The spelling of 21647977 in words is "twenty-one million, six hundred forty-seven thousand, nine hundred seventy-seven".