21061791 has 12 divisors (see below), whose sum is σ = 30478032. Its totient is φ = 14015616.

The previous prime is 21061783. The next prime is 21061819. The reversal of 21061791 is 19716012.

It is not a de Polignac number, because 21061791 - 2³ = 21061783 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21061771) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 4015 + ... + 7631.

It is an arithmetic number, because the mean of its divisors is an integer number (2539836).

Almost surely, 2^21061791 is an apocalyptic number.

21061791 is a deficient number, since it is larger than the sum of its proper divisors (9416241).

21061791 is a wasteful number, since it uses less digits than its factorization.

21061791 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 4270 (or 4267 counting only the distinct ones).

The product of its (nonzero) digits is 756, while the sum is 27.

The square root of 21061791 is about 4589.3126936394. The cubic root of 21061791 is about 276.1627505769.

It can be divided in two parts, 210 and 61791, that added together give a square (62001 = 249²).

The spelling of 21061791 in words is "twenty-one million, sixty-one thousand, seven hundred ninety-one".