21121081 has 2 divisors, whose sum is σ = 21121082. Its totient is φ = 21121080.

The previous prime is 21121069. The next prime is 21121091. The reversal of 21121081 is 18012112.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 21114025 + 7056 = 4595^2 + 84^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21121081 is a prime.

It is a super-2 number, since 2×21121081² = 892200125217122, which contains 22 as substring.

It is not a weakly prime, because it can be changed into another prime (21121091) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10560540 + 10560541.

It is an arithmetic number, because the mean of its divisors is an integer number (10560541).

Almost surely, 2^21121081 is an apocalyptic number.

It is an amenable number.

21121081 is a deficient number, since it is larger than the sum of its proper divisors (1).

21121081 is an equidigital number, since it uses as much as digits as its factorization.

21121081 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 32, while the sum is 16.

The square root of 21121081 is about 4595.7677269418. The cubic root of 21121081 is about 276.4216451348.

Adding to 21121081 its reverse (18012112), we get a palindrome (39133193).

The spelling of 21121081 in words is "twenty-one million, one hundred twenty-one thousand, eighty-one".