20961791 has 4 divisors (see below), whose sum is σ = 21077784. Its totient is φ = 20845800.

The previous prime is 20961779. The next prime is 20961793. The reversal of 20961791 is 19716902.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 19716902 = 2 ⋅9858451.

It is a cyclic number.

It is not a de Polignac number, because 20961791 - 2⁶ = 20961727 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (20961793) 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, 57725 + ... + 58086.

It is an arithmetic number, because the mean of its divisors is an integer number (5269446).

Almost surely, 2^20961791 is an apocalyptic number.

20961791 is a deficient number, since it is larger than the sum of its proper divisors (115993).

20961791 is a wasteful number, since it uses less digits than its factorization.

20961791 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 115992.

The product of its (nonzero) digits is 6804, while the sum is 35.

The square root of 20961791 is about 4578.4048532213. The cubic root of 20961791 is about 275.7249894915.

The spelling of 20961791 in words is "twenty million, nine hundred sixty-one thousand, seven hundred ninety-one".