21906651 has 16 divisors (see below), whose sum is σ = 32189696. Its totient is φ = 13166496.

The previous prime is 21906631. The next prime is 21906667. The reversal of 21906651 is 15660912.

It is not a de Polignac number, because 21906651 - 2¹⁰ = 21905627 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21906631) 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 15 ways as a sum of consecutive naturals, for example, 4855 + ... + 8208.

It is an arithmetic number, because the mean of its divisors is an integer number (2011856).

Almost surely, 2^21906651 is an apocalyptic number.

21906651 is a deficient number, since it is larger than the sum of its proper divisors (10283045).

21906651 is a wasteful number, since it uses less digits than its factorization.

21906651 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 13122.

The product of its (nonzero) digits is 3240, while the sum is 30.

The square root of 21906651 is about 4680.4541446317. The cubic root of 21906651 is about 279.8070567024.

The spelling of 21906651 in words is "twenty-one million, nine hundred six thousand, six hundred fifty-one".