21416991 has 16 divisors (see below), whose sum is σ = 30334464. Its totient is φ = 13394304.

The previous prime is 21416987. The next prime is 21416999. The reversal of 21416991 is 19961412.

It is not a de Polignac number, because 21416991 - 2² = 21416987 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21416999) 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 15 ways as a sum of consecutive naturals, for example, 23160 + ... + 24066.

It is an arithmetic number, because the mean of its divisors is an integer number (1895904).

Almost surely, 2^21416991 is an apocalyptic number.

21416991 is a deficient number, since it is larger than the sum of its proper divisors (8917473).

21416991 is a wasteful number, since it uses less digits than its factorization.

21416991 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1390.

The product of its digits is 3888, while the sum is 33.

The square root of 21416991 is about 4627.8495005780. The cubic root of 21416991 is about 277.7065680518.

It can be divided in two parts, 214 and 16991, that added together give a triangular number (17205 = T₁₈₅).

The spelling of 21416991 in words is "twenty-one million, four hundred sixteen thousand, nine hundred ninety-one".