21906745 has 32 divisors (see below), whose sum is σ = 31518720. Its totient is φ = 14300160.

The previous prime is 21906719. The next prime is 21906757. The reversal of 21906745 is 54760912.

It is not a de Polignac number, because 21906745 - 2⁷ = 21906617 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 21906745.

It is an unprimeable number.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 114600 + ... + 114790.

It is an arithmetic number, because the mean of its divisors is an integer number (984960).

Almost surely, 2^21906745 is an apocalyptic number.

It is an amenable number.

21906745 is a deficient number, since it is larger than the sum of its proper divisors (9611975).

21906745 is a wasteful number, since it uses less digits than its factorization.

21906745 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 345.

The product of its (nonzero) digits is 15120, while the sum is 34.

The square root of 21906745 is about 4680.4641863815. The cubic root of 21906745 is about 279.8074569131.

The spelling of 21906745 in words is "twenty-one million, nine hundred six thousand, seven hundred forty-five".