21623493 has 4 divisors (see below), whose sum is σ = 28831328. Its totient is φ = 14415660.

The previous prime is 21623479. The next prime is 21623509. The reversal of 21623493 is 39432612.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is not a de Polignac number, because 21623493 - 2⁴ = 21623477 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 21623493.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21623423) 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 3 ways as a sum of consecutive naturals, for example, 3603913 + ... + 3603918.

It is an arithmetic number, because the mean of its divisors is an integer number (7207832).

Almost surely, 2^21623493 is an apocalyptic number.

It is an amenable number.

21623493 is a deficient number, since it is larger than the sum of its proper divisors (7207835).

21623493 is an equidigital number, since it uses as much as digits as its factorization.

21623493 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 7207834.

The product of its digits is 7776, while the sum is 30.

The square root of 21623493 is about 4650.1067729677. The cubic root of 21623493 is about 278.5962608839.

The spelling of 21623493 in words is "twenty-one million, six hundred twenty-three thousand, four hundred ninety-three".