21945997 has 8 divisors (see below), whose sum is σ = 23358456. Its totient is φ = 20547072.

The previous prime is 21945977. The next prime is 21946003. The reversal of 21945997 is 79954912.

It is a happy number.

It can be written as a sum of positive squares in 4 ways, for example, as 10850436 + 11095561 = 3294^2 + 3331^2 .

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 21945997 - 2²³ = 13557389 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21945907) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 73 + ... + 6625.

It is an arithmetic number, because the mean of its divisors is an integer number (2919807).

Almost surely, 2^21945997 is an apocalyptic number.

It is an amenable number.

21945997 is a deficient number, since it is larger than the sum of its proper divisors (1412459).

21945997 is a wasteful number, since it uses less digits than its factorization.

21945997 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 6767.

The product of its digits is 204120, while the sum is 46.

The square root of 21945997 is about 4684.6554835975. The cubic root of 21945997 is about 279.9744747140.

The spelling of 21945997 in words is "twenty-one million, nine hundred forty-five thousand, nine hundred ninety-seven".