21177923 has 4 divisors (see below), whose sum is σ = 22807008. Its totient is φ = 19548840.

The previous prime is 21177907. The next prime is 21177931. The reversal of 21177923 is 32977112.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 21177923 - 2⁴ = 21177907 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 21177923.

It is not an unprimeable number, because it can be changed into a prime (21177943) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 814523 + ... + 814548.

It is an arithmetic number, because the mean of its divisors is an integer number (5701752).

Almost surely, 2^21177923 is an apocalyptic number.

21177923 is a deficient number, since it is larger than the sum of its proper divisors (1629085).

21177923 is a wasteful number, since it uses less digits than its factorization.

21177923 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1629084.

The product of its digits is 5292, while the sum is 32.

The square root of 21177923 is about 4601.9477398163. The cubic root of 21177923 is about 276.6693957893.

The spelling of 21177923 in words is "twenty-one million, one hundred seventy-seven thousand, nine hundred twenty-three".