21955945 has 16 divisors (see below), whose sum is σ = 28833408. Its totient is φ = 15917440.

The previous prime is 21955943. The next prime is 21955957. The reversal of 21955945 is 54955912.

It is not a de Polignac number, because 21955945 - 2¹ = 21955943 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 21955898 and 21955907.

It is not an unprimeable number, because it can be changed into a prime (21955943) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 33612 + ... + 34258.

It is an arithmetic number, because the mean of its divisors is an integer number (1802088).

Almost surely, 2^21955945 is an apocalyptic number.

It is an amenable number.

21955945 is a deficient number, since it is larger than the sum of its proper divisors (6877463).

21955945 is a wasteful number, since it uses less digits than its factorization.

21955945 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1280.

The product of its digits is 81000, while the sum is 40.

The square root of 21955945 is about 4685.7171276124. The cubic root of 21955945 is about 280.0167719545.

The spelling of 21955945 in words is "twenty-one million, nine hundred fifty-five thousand, nine hundred forty-five".