21287623 has 16 divisors (see below), whose sum is σ = 25090560. Its totient is φ = 17682336.

The previous prime is 21287551. The next prime is 21287633. The reversal of 21287623 is 32678212.

It is not a de Polignac number, because 21287623 - 2¹³ = 21279431 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21287633) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 59118 + ... + 59476.

It is an arithmetic number, because the mean of its divisors is an integer number (1568160).

Almost surely, 2^21287623 is an apocalyptic number.

21287623 is a deficient number, since it is larger than the sum of its proper divisors (3802937).

21287623 is a wasteful number, since it uses less digits than its factorization.

21287623 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 606.

The product of its digits is 8064, while the sum is 31.

The square root of 21287623 is about 4613.8512112984. The cubic root of 21287623 is about 277.1462820002.

The spelling of 21287623 in words is "twenty-one million, two hundred eighty-seven thousand, six hundred twenty-three".