21909986 has 8 divisors (see below), whose sum is σ = 37560000. Its totient is φ = 9389988.

The previous prime is 21909977. The next prime is 21909989. The reversal of 21909986 is 68990912.

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

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (21909989) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 782486 + ... + 782513.

It is an arithmetic number, because the mean of its divisors is an integer number (4695000).

Almost surely, 2^21909986 is an apocalyptic number.

21909986 is a deficient number, since it is larger than the sum of its proper divisors (15650014).

21909986 is a wasteful number, since it uses less digits than its factorization.

21909986 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1565008.

The product of its (nonzero) digits is 69984, while the sum is 44.

The square root of 21909986 is about 4680.8103999201. The cubic root of 21909986 is about 279.8212549655.

The spelling of 21909986 in words is "twenty-one million, nine hundred nine thousand, nine hundred eighty-six".