21992945 has 32 divisors (see below), whose sum is σ = 30385152. Its totient is φ = 15155712.

The previous prime is 21992941. The next prime is 21992947. The reversal of 21992945 is 54929912.

It is a happy number.

It is not a de Polignac number, because 21992945 - 2² = 21992941 is a prime.

It is a Duffinian number.

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (21992941) by changing a digit.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 70109 + ... + 70421.

It is an arithmetic number, because the mean of its divisors is an integer number (949536).

Almost surely, 2^21992945 is an apocalyptic number.

It is an amenable number.

21992945 is a deficient number, since it is larger than the sum of its proper divisors (8392207).

21992945 is a wasteful number, since it uses less digits than its factorization.

21992945 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 401.

The product of its digits is 58320, while the sum is 41.

The square root of 21992945 is about 4689.6636339934. The cubic root of 21992945 is about 280.1739777610.

The spelling of 21992945 in words is "twenty-one million, nine hundred ninety-two thousand, nine hundred forty-five".