21891473 has 2 divisors, whose sum is σ = 21891474. Its totient is φ = 21891472.

The previous prime is 21891449. The next prime is 21891479. The reversal of 21891473 is 37419812.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 16265089 + 5626384 = 4033^2 + 2372^2 .

It is a cyclic number.

It is not a de Polignac number, because 21891473 - 2¹² = 21887377 is a prime.

It is not a weakly prime, because it can be changed into another prime (21891479) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10945736 + 10945737.

It is an arithmetic number, because the mean of its divisors is an integer number (10945737).

Almost surely, 2^21891473 is an apocalyptic number.

It is an amenable number.

21891473 is a deficient number, since it is larger than the sum of its proper divisors (1).

21891473 is an equidigital number, since it uses as much as digits as its factorization.

21891473 is an evil number, because the sum of its binary digits is even.

The product of its digits is 12096, while the sum is 35.

The square root of 21891473 is about 4678.8324398294. The cubic root of 21891473 is about 279.7424204312.

The spelling of 21891473 in words is "twenty-one million, eight hundred ninety-one thousand, four hundred seventy-three".