21987445 has 8 divisors (see below), whose sum is σ = 26412120. Its totient is φ = 17571840.

The previous prime is 21987403. The next prime is 21987461. The reversal of 21987445 is 54478912.

It can be written as a sum of positive squares in 4 ways, for example, as 3247204 + 18740241 = 1802^2 + 4329^2 .

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

It is not a de Polignac number, because 21987445 - 2¹³ = 21979253 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 21987398 and 21987407.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 5485 + ... + 8605.

It is an arithmetic number, because the mean of its divisors is an integer number (3301515).

Almost surely, 2^21987445 is an apocalyptic number.

It is an amenable number.

21987445 is a deficient number, since it is larger than the sum of its proper divisors (4424675).

21987445 is a wasteful number, since it uses less digits than its factorization.

21987445 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4535.

The product of its digits is 80640, while the sum is 40.

The square root of 21987445 is about 4689.0772013265. The cubic root of 21987445 is about 280.1506204928.

The spelling of 21987445 in words is "twenty-one million, nine hundred eighty-seven thousand, four hundred forty-five".