21691058 has 4 divisors (see below), whose sum is σ = 32536590. Its totient is φ = 10845528.

The previous prime is 21691037. The next prime is 21691067. The reversal of 21691058 is 85019612.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in only one way, i.e., 20857489 + 833569 = 4567^2 + 913^2 .

It is an unprimeable number.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 5422763 + ... + 5422766.

Almost surely, 2^21691058 is an apocalyptic number.

21691058 is a deficient number, since it is larger than the sum of its proper divisors (10845532).

21691058 is a wasteful number, since it uses less digits than its factorization.

21691058 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 10845531.

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

The square root of 21691058 is about 4657.3659937780. The cubic root of 21691058 is about 278.8861274827.

The spelling of 21691058 in words is "twenty-one million, six hundred ninety-one thousand, fifty-eight".