21065121 has 48 divisors (see below), whose sum is σ = 38413440. Its totient is φ = 10805760.

The previous prime is 21065117. The next prime is 21065123. The reversal of 21065121 is 12156012.

21065121 is a `hidden beast` number, since 2 + 10 + 651 + 2 + 1 = 666.

It is not a de Polignac number, because 21065121 - 2² = 21065117 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 21065094 and 21065103.

It is not an unprimeable number, because it can be changed into a prime (21065123) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 47 ways as a sum of consecutive naturals, for example, 78175 + ... + 78443.

It is an arithmetic number, because the mean of its divisors is an integer number (800280).

Almost surely, 2^21065121 is an apocalyptic number.

21065121 is a gapful number since it is divisible by the number (21) formed by its first and last digit.

It is an amenable number.

21065121 is a deficient number, since it is larger than the sum of its proper divisors (17348319).

21065121 is a wasteful number, since it uses less digits than its factorization.

21065121 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 406 (or 403 counting only the distinct ones).

The product of its (nonzero) digits is 120, while the sum is 18.

The square root of 21065121 is about 4589.6754787240. The cubic root of 21065121 is about 276.1773041587.

It can be divided in two parts, 2106 and 5121, that added together give a palindrome (7227).

The spelling of 21065121 in words is "twenty-one million, sixty-five thousand, one hundred twenty-one".