21891471 has 8 divisors (see below), whose sum is σ = 33358464. Its totient is φ = 12509400.

The previous prime is 21891449. The next prime is 21891473. The reversal of 21891471 is 17419812.

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

It is not a de Polignac number, because 21891471 - 2⁹ = 21890959 is a prime.

It is a super-3 number, since 3×21891471³ (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 (21891473) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 521205 + ... + 521246.

It is an arithmetic number, because the mean of its divisors is an integer number (4169808).

Almost surely, 2^21891471 is an apocalyptic number.

21891471 is a gapful number since it is divisible by the number (21) formed by its first and last digit.

21891471 is a deficient number, since it is larger than the sum of its proper divisors (11466993).

21891471 is a wasteful number, since it uses less digits than its factorization.

21891471 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1042461.

The product of its digits is 4032, while the sum is 33.

The square root of 21891471 is about 4678.8322261009. The cubic root of 21891471 is about 279.7424119121.

The spelling of 21891471 in words is "twenty-one million, eight hundred ninety-one thousand, four hundred seventy-one".