20687691 has 8 divisors (see below), whose sum is σ = 29206224. Its totient is φ = 12980480.

The previous prime is 20687683. The next prime is 20687707. The reversal of 20687691 is 19678602.

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 20687691 - 2³ = 20687683 is a prime.

It is a super-2 number, since 2×20687691² = 855961117822962, which contains 22 as substring.

It is not an unprimeable number, because it can be changed into a prime (20687291) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 202770 + ... + 202871.

It is an arithmetic number, because the mean of its divisors is an integer number (3650778).

Almost surely, 2^20687691 is an apocalyptic number.

20687691 is a deficient number, since it is larger than the sum of its proper divisors (8518533).

20687691 is a wasteful number, since it uses less digits than its factorization.

20687691 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 405661.

The product of its (nonzero) digits is 36288, while the sum is 39.

The square root of 20687691 is about 4548.3723462355. The cubic root of 20687691 is about 274.5179035506.

The spelling of 20687691 in words is "twenty million, six hundred eighty-seven thousand, six hundred ninety-one".