20691631 has 4 divisors (see below), whose sum is σ = 20975152. Its totient is φ = 20408112.

The previous prime is 20691613. The next prime is 20691647. The reversal of 20691631 is 13619602.

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 20691631 - 2¹¹ = 20689583 is a prime.

It is a super-2 number, since 2×20691631² = 856287186880322, which contains 22 as substring.

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 20691631.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (20691661) 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, 141651 + ... + 141796.

It is an arithmetic number, because the mean of its divisors is an integer number (5243788).

Almost surely, 2^20691631 is an apocalyptic number.

20691631 is a deficient number, since it is larger than the sum of its proper divisors (283521).

20691631 is an equidigital number, since it uses as much as digits as its factorization.

20691631 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 283520.

The product of its (nonzero) digits is 1944, while the sum is 28.

The square root of 20691631 is about 4548.8054475873. The cubic root of 20691631 is about 274.5353298853.

The spelling of 20691631 in words is "twenty million, six hundred ninety-one thousand, six hundred thirty-one".