21623389 has 2 divisors, whose sum is σ = 21623390. Its totient is φ = 21623388.

The previous prime is 21623369. The next prime is 21623411. The reversal of 21623389 is 98332612.

It is a happy number.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 15288100 + 6335289 = 3910^2 + 2517^2 .

It is a cyclic number.

It is not a de Polignac number, because 21623389 - 2²¹ = 19526237 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21623369) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10811694 + 10811695.

It is an arithmetic number, because the mean of its divisors is an integer number (10811695).

Almost surely, 2^21623389 is an apocalyptic number.

It is an amenable number.

21623389 is a deficient number, since it is larger than the sum of its proper divisors (1).

21623389 is an equidigital number, since it uses as much as digits as its factorization.

21623389 is an evil number, because the sum of its binary digits is even.

The product of its digits is 15552, while the sum is 34.

The square root of 21623389 is about 4650.0955904153. The cubic root of 21623389 is about 278.5958142392.

The spelling of 21623389 in words is "twenty-one million, six hundred twenty-three thousand, three hundred eighty-nine".