21987746 has 16 divisors (see below), whose sum is σ = 36475488. Its totient is φ = 9856800.

The previous prime is 21987737. The next prime is 21987787. The reversal of 21987746 is 64778912.

It is a junction number, because it is equal to n+sod(n) for n = 21987697 and 21987706.

It is an unprimeable number.

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, 5240 + ... + 8451.

It is an arithmetic number, because the mean of its divisors is an integer number (2279718).

Almost surely, 2^21987746 is an apocalyptic number.

21987746 is a deficient number, since it is larger than the sum of its proper divisors (14487742).

21987746 is a wasteful number, since it uses less digits than its factorization.

21987746 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 13777.

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

The square root of 21987746 is about 4689.1092970840. The cubic root of 21987746 is about 280.1518988731.

The spelling of 21987746 in words is "twenty-one million, nine hundred eighty-seven thousand, seven hundred forty-six".