21437665 has 8 divisors (see below), whose sum is σ = 25770600. Its totient is φ = 17119872.

The previous prime is 21437639. The next prime is 21437701. The reversal of 21437665 is 56673412.

It is a happy number.

It can be written as a sum of positive squares in 4 ways, for example, as 1079521 + 20358144 = 1039^2 + 4512^2 .

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 21437665 - 2¹⁹ = 20913377 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 21437665.

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, 390 + ... + 6559.

It is an arithmetic number, because the mean of its divisors is an integer number (3221325).

Almost surely, 2^21437665 is an apocalyptic number.

It is an amenable number.

21437665 is a deficient number, since it is larger than the sum of its proper divisors (4332935).

21437665 is an equidigital number, since it uses as much as digits as its factorization.

21437665 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 7571.

The product of its digits is 30240, while the sum is 34.

The square root of 21437665 is about 4630.0826126539. The cubic root of 21437665 is about 277.7958968033.

The spelling of 21437665 in words is "twenty-one million, four hundred thirty-seven thousand, six hundred sixty-five".