21987706 has 32 divisors (see below), whose sum is σ = 36989568. Its totient is φ = 9737280.

The previous prime is 21987703. The next prime is 21987727. The reversal of 21987706 is 60778912.

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 15 ways as a sum of consecutive naturals, for example, 79240 + ... + 79516.

It is an arithmetic number, because the mean of its divisors is an integer number (1155924).

Almost surely, 2^21987706 is an apocalyptic number.

21987706 is a gapful number since it is divisible by the number (26) formed by its first and last digit.

21987706 is a deficient number, since it is larger than the sum of its proper divisors (15001862).

21987706 is a wasteful number, since it uses less digits than its factorization.

21987706 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 406.

The product of its (nonzero) digits is 42336, while the sum is 40.

The square root of 21987706 is about 4689.1050318798. The cubic root of 21987706 is about 280.1517289893.

The spelling of 21987706 in words is "twenty-one million, nine hundred eighty-seven thousand, seven hundred six".