21173121 has 6 divisors (see below), whose sum is σ = 30583410. Its totient is φ = 14115408.

The previous prime is 21173107. The next prime is 21173147. The reversal of 21173121 is 12137112.

It is a happy number.

It can be written as a sum of positive squares in only one way, i.e., 12173121 + 9000000 = 3489^2 + 3000^2 .

It is not a de Polignac number, because 21173121 - 2⁶ = 21173057 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 21173094 and 21173103.

It is not an unprimeable number, because it can be changed into a prime (21173101) by changing a digit.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 1176276 + ... + 1176293.

It is an arithmetic number, because the mean of its divisors is an integer number (5097235).

Almost surely, 2^21173121 is an apocalyptic number.

It is an amenable number.

21173121 is a deficient number, since it is larger than the sum of its proper divisors (9410289).

21173121 is a wasteful number, since it uses less digits than its factorization.

21173121 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2352575 (or 2352572 counting only the distinct ones).

The product of its digits is 84, while the sum is 18.

The square root of 21173121 is about 4601.4259746300. The cubic root of 21173121 is about 276.6484830229.

The spelling of 21173121 in words is "twenty-one million, one hundred seventy-three thousand, one hundred twenty-one".