20691641 has 4 divisors (see below), whose sum is σ = 20706384. Its totient is φ = 20676900.

The previous prime is 20691613. The next prime is 20691647. The reversal of 20691641 is 14619602.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4, and also an emirpimes, since its reverse is a distinct semiprime: 14619602 = 2 ⋅7309801.

It is a cyclic number.

It is not a de Polignac number, because 20691641 - 2⁶ = 20691577 is a prime.

It is a Duffinian number.

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (20691647) 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, 5015 + ... + 8156.

It is an arithmetic number, because the mean of its divisors is an integer number (5176596).

Almost surely, 2^20691641 is an apocalyptic number.

It is an amenable number.

20691641 is a deficient number, since it is larger than the sum of its proper divisors (14743).

20691641 is a wasteful number, since it uses less digits than its factorization.

20691641 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 14742.

The product of its (nonzero) digits is 2592, while the sum is 29.

The square root of 20691641 is about 4548.8065467769. The cubic root of 20691641 is about 274.5353741117.

The spelling of 20691641 in words is "twenty million, six hundred ninety-one thousand, six hundred forty-one".