21996691 has 4 divisors (see below), whose sum is σ = 23290632. Its totient is φ = 20702752.

The previous prime is 21996683. The next prime is 21996697. The reversal of 21996691 is 19669912.

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

It is a cyclic number.

It is not a de Polignac number, because 21996691 - 2³ = 21996683 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21996697) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 646945 + ... + 646978.

It is an arithmetic number, because the mean of its divisors is an integer number (5822658).

Almost surely, 2^21996691 is an apocalyptic number.

21996691 is a deficient number, since it is larger than the sum of its proper divisors (1293941).

21996691 is a wasteful number, since it uses less digits than its factorization.

21996691 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1293940.

The product of its digits is 52488, while the sum is 43.

The square root of 21996691 is about 4690.0630059734. The cubic root of 21996691 is about 280.1898839549.

The spelling of 21996691 in words is "twenty-one million, nine hundred ninety-six thousand, six hundred ninety-one".