21121807 has 8 divisors (see below), whose sum is σ = 24169376. Its totient is φ = 18081792.

The previous prime is 21121781. The next prime is 21121811. The reversal of 21121807 is 70812112.

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 21121807 - 2⁷ = 21121679 is a prime.

It is a super-2 number, since 2×21121807² = 892261461890498, which contains 22 as substring.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21121207) 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 7 ways as a sum of consecutive naturals, for example, 6763 + ... + 9379.

It is an arithmetic number, because the mean of its divisors is an integer number (3021172).

Almost surely, 2^21121807 is an apocalyptic number.

21121807 is a deficient number, since it is larger than the sum of its proper divisors (3047569).

21121807 is a wasteful number, since it uses less digits than its factorization.

21121807 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3777.

The product of its (nonzero) digits is 224, while the sum is 22.

The square root of 21121807 is about 4595.8467119781. The cubic root of 21121807 is about 276.4248122678.

Adding to 21121807 its reverse (70812112), we get a palindrome (91933919).

The spelling of 21121807 in words is "twenty-one million, one hundred twenty-one thousand, eight hundred seven".