21658394 has 12 divisors (see below), whose sum is σ = 33427422. Its totient is φ = 10517040.

The previous prime is 21658393. The next prime is 21658421. The reversal of 21658394 is 49385612.

It is a happy number.

It can be written as a sum of positive squares in 3 ways, for example, as 20133169 + 1525225 = 4487^2 + 1235^2 .

It is not an unprimeable number, because it can be changed into a prime (21658393) 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 5 ways as a sum of consecutive naturals, for example, 39764 + ... + 40304.

Almost surely, 2^21658394 is an apocalyptic number.

21658394 is a deficient number, since it is larger than the sum of its proper divisors (11769028).

21658394 is an frugal number, since it uses more digits than its factorization.

21658394 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1121 (or 580 counting only the distinct ones).

The product of its digits is 51840, while the sum is 38.

The square root of 21658394 is about 4653.8579694701. The cubic root of 21658394 is about 278.7460680336.

The spelling of 21658394 in words is "twenty-one million, six hundred fifty-eight thousand, three hundred ninety-four".