21326991 has 8 divisors (see below), whose sum is σ = 32498304. Its totient is φ = 12186840.

The previous prime is 21326989. The next prime is 21327001. The reversal of 21326991 is 19962312.

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

It is not a de Polignac number, because 21326991 - 2¹ = 21326989 is a prime.

It is a super-2 number, since 2×21326991² = 909681090228162, which contains 22 as substring.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21326941) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 507765 + ... + 507806.

It is an arithmetic number, because the mean of its divisors is an integer number (4062288).

Almost surely, 2^21326991 is an apocalyptic number.

21326991 is a gapful number since it is divisible by the number (21) formed by its first and last digit.

21326991 is a deficient number, since it is larger than the sum of its proper divisors (11171313).

21326991 is a wasteful number, since it uses less digits than its factorization.

21326991 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1015581.

The product of its digits is 5832, while the sum is 33.

The square root of 21326991 is about 4618.1155247568. The cubic root of 21326991 is about 277.3170224641.

The spelling of 21326991 in words is "twenty-one million, three hundred twenty-six thousand, nine hundred ninety-one".