21845691 has 24 divisors (see below), whose sum is σ = 36351744. Its totient is φ = 12383280.

The previous prime is 21845689. The next prime is 21845693. The reversal of 21845691 is 19654812.

It is an interprime number because it is at equal distance from previous prime (21845689) and next prime (21845693).

It is not a de Polignac number, because 21845691 - 2¹ = 21845689 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21845693) by changing a digit.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 6930 + ... + 9576.

It is an arithmetic number, because the mean of its divisors is an integer number (1514656).

Almost surely, 2^21845691 is an apocalyptic number.

21845691 is a gapful number since it is divisible by the number (21) formed by its first and last digit.

21845691 is a deficient number, since it is larger than the sum of its proper divisors (14506053).

21845691 is a wasteful number, since it uses less digits than its factorization.

21845691 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2791 (or 2788 counting only the distinct ones).

The product of its digits is 17280, while the sum is 36.

The square root of 21845691 is about 4673.9374193500. The cubic root of 21845691 is about 279.5472743450.

It can be divided in two parts, 2184 and 5691, that added together give a triangular number (7875 = T₁₂₅).

The spelling of 21845691 in words is "twenty-one million, eight hundred forty-five thousand, six hundred ninety-one".