21980605 has 4 divisors (see below), whose sum is σ = 26376732. Its totient is φ = 17584480.

The previous prime is 21980593. The next prime is 21980653. The reversal of 21980605 is 50608912.

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 9406489 + 12574116 = 3067^2 + 3546^2 .

It is not a de Polignac number, because 21980605 - 2¹⁵ = 21947837 is a prime.

It is a Smith number, since the sum of its digits (31) coincides with the sum of the digits of its prime factors. Since it is squarefree, it is also a hoax number.

It is a Duffinian number.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 2198056 + ... + 2198065.

It is an arithmetic number, because the mean of its divisors is an integer number (6594183).

Almost surely, 2^21980605 is an apocalyptic number.

It is an amenable number.

21980605 is a deficient number, since it is larger than the sum of its proper divisors (4396127).

21980605 is an equidigital number, since it uses as much as digits as its factorization.

21980605 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4396126.

The product of its (nonzero) digits is 4320, while the sum is 31.

The square root of 21980605 is about 4688.3477900002. The cubic root of 21980605 is about 280.1215671097.

The spelling of 21980605 in words is "twenty-one million, nine hundred eighty thousand, six hundred five".