21987705 has 8 divisors (see below), whose sum is σ = 35180352. Its totient is φ = 11726768.

The previous prime is 21987703. The next prime is 21987727. The reversal of 21987705 is 50778912.

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 21987705 - 2¹ = 21987703 is a prime.

It is not an unprimeable number, because it can be changed into a prime (21987703) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 732909 + ... + 732938.

It is an arithmetic number, because the mean of its divisors is an integer number (4397544).

Almost surely, 2^21987705 is an apocalyptic number.

It is an amenable number.

21987705 is a deficient number, since it is larger than the sum of its proper divisors (13192647).

21987705 is a wasteful number, since it uses less digits than its factorization.

21987705 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1465855.

The product of its (nonzero) digits is 35280, while the sum is 39.

The square root of 21987705 is about 4689.1049252496. The cubic root of 21987705 is about 280.1517247422.

The spelling of 21987705 in words is "twenty-one million, nine hundred eighty-seven thousand, seven hundred five".