21494991 has 8 divisors (see below), whose sum is σ = 32754304. Its totient is φ = 12282840.

The previous prime is 21494959. The next prime is 21494999. The reversal of 21494991 is 19949412.

It is a sphenic number, since it is the product of 3 distinct primes.

It is not a de Polignac number, because 21494991 - 2⁵ = 21494959 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 (21494999) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 511765 + ... + 511806.

It is an arithmetic number, because the mean of its divisors is an integer number (4094288).

Almost surely, 2^21494991 is an apocalyptic number.

21494991 is a gapful number since it is divisible by the number (21) formed by its first and last digit.

21494991 is a deficient number, since it is larger than the sum of its proper divisors (11259313).

21494991 is a wasteful number, since it uses less digits than its factorization.

21494991 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1023581.

The product of its digits is 23328, while the sum is 39.

The square root of 21494991 is about 4636.2690819235. The cubic root of 21494991 is about 278.0432924314.

It can be divided in two parts, 2149 and 4991, that added together give a triangular number (7140 = T₁₁₉).

The spelling of 21494991 in words is "twenty-one million, four hundred ninety-four thousand, nine hundred ninety-one".