21861791 has 8 divisors (see below), whose sum is σ = 25495200. Its totient is φ = 18738384.

The previous prime is 21861773. The next prime is 21861797. The reversal of 21861791 is 19716812.

It is not a de Polignac number, because 21861791 - 2¹⁸ = 21599647 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 (21861797) 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, 31526 + ... + 32211.

It is an arithmetic number, because the mean of its divisors is an integer number (3186900).

Almost surely, 2^21861791 is an apocalyptic number.

21861791 is a deficient number, since it is larger than the sum of its proper divisors (3633409).

21861791 is an frugal number, since it uses more digits than its factorization.

21861791 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 63758 (or 63744 counting only the distinct ones).

The product of its digits is 6048, while the sum is 35.

The square root of 21861791 is about 4675.6594187344. The cubic root of 21861791 is about 279.6159317584.

The spelling of 21861791 in words is "twenty-one million, eight hundred sixty-one thousand, seven hundred ninety-one".