21091658 has 24 divisors (see below), whose sum is σ = 36965412. Its totient is φ = 8999424.

The previous prime is 21091649. The next prime is 21091663. The reversal of 21091658 is 85619012.

It can be written as a sum of positive squares in 2 ways, for example, as 18292729 + 2798929 = 4277^2 + 1673^2 .

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 11 ways as a sum of consecutive naturals, for example, 36266 + ... + 36842.

Almost surely, 2^21091658 is an apocalyptic number.

21091658 is a deficient number, since it is larger than the sum of its proper divisors (15873754).

21091658 is a wasteful number, since it uses less digits than its factorization.

21091658 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 966 (or 959 counting only the distinct ones).

The product of its (nonzero) digits is 4320, while the sum is 32.

The square root of 21091658 is about 4592.5655139584. The cubic root of 21091658 is about 276.2932278811.

The spelling of 21091658 in words is "twenty-one million, ninety-one thousand, six hundred fifty-eight".