21905073 has 20 divisors (see below), whose sum is σ = 33611380. Its totient is φ = 14206752.

The previous prime is 21905071. The next prime is 21905077. The reversal of 21905073 is 37050912.

It can be written as a sum of positive squares in 2 ways, for example, as 15186609 + 6718464 = 3897^2 + 2592^2 .

It is not a de Polignac number, because 21905073 - 2¹ = 21905071 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (27).

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21905071) by changing a digit.

It is a polite number, since it can be written in 19 ways as a sum of consecutive naturals, for example, 658 + ... + 6651.

It is an arithmetic number, because the mean of its divisors is an integer number (1680569).

Almost surely, 2^21905073 is an apocalyptic number.

It is an amenable number.

21905073 is a deficient number, since it is larger than the sum of its proper divisors (11706307).

21905073 is an equidigital number, since it uses as much as digits as its factorization.

21905073 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 7358 (or 7349 counting only the distinct ones).

The product of its (nonzero) digits is 1890, while the sum is 27.

The square root of 21905073 is about 4680.2855682106. The cubic root of 21905073 is about 279.8003381015.

Adding to 21905073 its reverse (37050912), we get a palindrome (58955985).

The spelling of 21905073 in words is "twenty-one million, nine hundred five thousand, seventy-three".