21909471 has 8 divisors (see below), whose sum is σ = 30220080. Its totient is φ = 14102592.

The previous prime is 21909463. The next prime is 21909479. The reversal of 21909471 is 17490912.

It is an interprime number because it is at equal distance from previous prime (21909463) and next prime (21909479).

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

It is not a de Polignac number, because 21909471 - 2³ = 21909463 is a prime.

It is a super-3 number, since 3×21909471³ (a number of 23 digits) contains 333 as substring.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21909479) 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, 125830 + ... + 126003.

It is an arithmetic number, because the mean of its divisors is an integer number (3777510).

Almost surely, 2^21909471 is an apocalyptic number.

21909471 is a deficient number, since it is larger than the sum of its proper divisors (8310609).

21909471 is a wasteful number, since it uses less digits than its factorization.

21909471 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 251865.

The product of its (nonzero) digits is 4536, while the sum is 33.

The square root of 21909471 is about 4680.7553877553. The cubic root of 21909471 is about 279.8190625242.

The spelling of 21909471 in words is "twenty-one million, nine hundred nine thousand, four hundred seventy-one".