21769399 has 4 divisors (see below), whose sum is σ = 21828136. Its totient is φ = 21710664.

The previous prime is 21769393. The next prime is 21769411. The reversal of 21769399 is 99396712.

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 21769399 - 2⁷ = 21769271 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 (21769393) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 28809 + ... + 29554.

It is an arithmetic number, because the mean of its divisors is an integer number (5457034).

Almost surely, 2^21769399 is an apocalyptic number.

21769399 is a deficient number, since it is larger than the sum of its proper divisors (58737).

21769399 is an equidigital number, since it uses as much as digits as its factorization.

21769399 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 58736.

The product of its digits is 183708, while the sum is 46.

The square root of 21769399 is about 4665.7688541118. The cubic root of 21769399 is about 279.2214725496.

It can be divided in two parts, 21 and 769399, that added together give a triangular number (769420 = T₁₂₄₀).

The spelling of 21769399 in words is "twenty-one million, seven hundred sixty-nine thousand, three hundred ninety-nine".