21661736 has 32 divisors (see below), whose sum is σ = 42301440. Its totient is φ = 10390848.

The previous prime is 21661733. The next prime is 21661781. The reversal of 21661736 is 63716612.

It is not an unprimeable number, because it can be changed into a prime (21661733) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 19385 + ... + 20471.

It is an arithmetic number, because the mean of its divisors is an integer number (1321920).

Almost surely, 2^21661736 is an apocalyptic number.

It is an amenable number.

21661736 is a deficient number, since it is larger than the sum of its proper divisors (20639704).

21661736 is a wasteful number, since it uses less digits than its factorization.

21661736 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1193 (or 1189 counting only the distinct ones).

The product of its digits is 9072, while the sum is 32.

The square root of 21661736 is about 4654.2170125597. The cubic root of 21661736 is about 278.7604046067.

The spelling of 21661736 in words is "twenty-one million, six hundred sixty-one thousand, seven hundred thirty-six".