20891207 has 4 divisors (see below), whose sum is σ = 20910480. Its totient is φ = 20871936.

The previous prime is 20891197. The next prime is 20891209. The reversal of 20891207 is 70219802.

It is a happy number.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 70219802 = 2 ⋅35109901.

It is a cyclic number.

It is not a de Polignac number, because 20891207 - 2¹⁰ = 20890183 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 20891207.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (20891209) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 7907 + ... + 10212.

It is an arithmetic number, because the mean of its divisors is an integer number (5227620).

Almost surely, 2^20891207 is an apocalyptic number.

20891207 is a deficient number, since it is larger than the sum of its proper divisors (19273).

20891207 is a wasteful number, since it uses less digits than its factorization.

20891207 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 19272.

The product of its (nonzero) digits is 2016, while the sum is 29.

The square root of 20891207 is about 4570.6899916752. The cubic root of 20891207 is about 275.4151613545.

The spelling of 20891207 in words is "twenty million, eight hundred ninety-one thousand, two hundred seven".