21993767 has 6 divisors (see below), whose sum is σ = 23363928. Its totient is φ = 20699744.

The previous prime is 21993757. The next prime is 21993779. The reversal of 21993767 is 76739912.

It is a happy number.

It is not a de Polignac number, because 21993767 - 2⁶ = 21993703 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 (21993707) by changing a digit.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 37763 + ... + 38340.

It is an arithmetic number, because the mean of its divisors is an integer number (3893988).

Almost surely, 2^21993767 is an apocalyptic number.

21993767 is a deficient number, since it is larger than the sum of its proper divisors (1370161).

21993767 is an equidigital number, since it uses as much as digits as its factorization.

21993767 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 76137 (or 76120 counting only the distinct ones).

The product of its digits is 142884, while the sum is 44.

The square root of 21993767 is about 4689.7512727223. The cubic root of 21993767 is about 280.1774682764.

The spelling of 21993767 in words is "twenty-one million, nine hundred ninety-three thousand, seven hundred sixty-seven".