21906145 has 16 divisors (see below), whose sum is σ = 27800640. Its totient is φ = 16524864.

The previous prime is 21906113. The next prime is 21906151. The reversal of 21906145 is 54160912.

It is a cyclic number.

It is not a de Polignac number, because 21906145 - 2⁵ = 21906113 is a prime.

It is a super-2 number, since 2×21906145² = 959758377522050, which contains 22 as substring.

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 15 ways as a sum of consecutive naturals, for example, 27442 + ... + 28228.

It is an arithmetic number, because the mean of its divisors is an integer number (1737540).

Almost surely, 2^21906145 is an apocalyptic number.

It is an amenable number.

21906145 is a deficient number, since it is larger than the sum of its proper divisors (5894495).

21906145 is a wasteful number, since it uses less digits than its factorization.

21906145 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1104.

The product of its (nonzero) digits is 2160, while the sum is 28.

The square root of 21906145 is about 4680.4000897359. The cubic root of 21906145 is about 279.8049023573.

The spelling of 21906145 in words is "twenty-one million, nine hundred six thousand, one hundred forty-five".