21403623 has 8 divisors (see below), whose sum is σ = 28605808. Its totient is φ = 14235264.

The previous prime is 21403621. The next prime is 21403643. The reversal of 21403623 is 32630412.

It is a happy number.

It is a sphenic number, since it is the product of 3 distinct primes.

It is not a de Polignac number, because 21403623 - 2¹ = 21403621 is a prime.

It is a super-2 number, since 2×21403623² = 916230155052258, which contains 22 as substring.

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 21403623.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21403621) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 6940 + ... + 9537.

It is an arithmetic number, because the mean of its divisors is an integer number (3575726).

Almost surely, 2^21403623 is an apocalyptic number.

21403623 is a deficient number, since it is larger than the sum of its proper divisors (7202185).

21403623 is a wasteful number, since it uses less digits than its factorization.

21403623 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 16913.

The product of its (nonzero) digits is 864, while the sum is 21.

The square root of 21403623 is about 4626.4049757884. The cubic root of 21403623 is about 277.6487766458.

The spelling of 21403623 in words is "twenty-one million, four hundred three thousand, six hundred twenty-three".