21520623 has 8 divisors (see below), whose sum is σ = 30382128. Its totient is φ = 13503104.

The previous prime is 21520607. The next prime is 21520637. The reversal of 21520623 is 32602512.

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

It is a cyclic number.

It is not a de Polignac number, because 21520623 - 2⁴ = 21520607 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 21520623.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21520693) 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, 210936 + ... + 211037.

It is an arithmetic number, because the mean of its divisors is an integer number (3797766).

Almost surely, 2^21520623 is an apocalyptic number.

21520623 is a deficient number, since it is larger than the sum of its proper divisors (8861505).

21520623 is a wasteful number, since it uses less digits than its factorization.

21520623 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 421993.

The product of its (nonzero) digits is 720, while the sum is 21.

The square root of 21520623 is about 4639.0325500044. The cubic root of 21520623 is about 278.1537673901.

The spelling of 21520623 in words is "twenty-one million, five hundred twenty thousand, six hundred twenty-three".