21445957 has 4 divisors (see below), whose sum is σ = 23095660. Its totient is φ = 19796256.

The previous prime is 21445943. The next prime is 21445961. The reversal of 21445957 is 75954412.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 13905441 + 7540516 = 3729^2 + 2746^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21445957 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 (21445157) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 824832 + ... + 824857.

It is an arithmetic number, because the mean of its divisors is an integer number (5773915).

Almost surely, 2^21445957 is an apocalyptic number.

It is an amenable number.

21445957 is a deficient number, since it is larger than the sum of its proper divisors (1649703).

21445957 is a wasteful number, since it uses less digits than its factorization.

21445957 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1649702.

The product of its digits is 50400, while the sum is 37.

The square root of 21445957 is about 4630.9779744672. The cubic root of 21445957 is about 277.8317089536.

The spelling of 21445957 in words is "twenty-one million, four hundred forty-five thousand, nine hundred fifty-seven".