21100021007 has 4 divisors (see below), whose sum is σ = 22723099560. Its totient is φ = 19476942456.

The previous prime is 21100021001. The next prime is 21100021021. The reversal of 21100021007 is 70012000112.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 21100021007 - 2²⁰ = 21098972431 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 21100020982 and 21100021000.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21100021001) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 811539257 + ... + 811539282.

It is an arithmetic number, because the mean of its divisors is an integer number (5680774890).

Almost surely, 2^21100021007 is an apocalyptic number.

21100021007 is a deficient number, since it is larger than the sum of its proper divisors (1623078553).

21100021007 is a wasteful number, since it uses less digits than its factorization.

21100021007 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1623078552.

The product of its (nonzero) digits is 28, while the sum is 14.

Adding to 21100021007 its reverse (70012000112), we get a palindrome (91112021119).

The spelling of 21100021007 in words is "twenty-one billion, one hundred million, twenty-one thousand, seven".