21328777 has 4 divisors (see below), whose sum is σ = 21338640. Its totient is φ = 21318916.

The previous prime is 21328763. The next prime is 21328781. The reversal of 21328777 is 77782312.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4, and also a brilliant number, because the two primes have the same length.

It is a cyclic number.

It is not a de Polignac number, because 21328777 - 2⁷ = 21328649 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21328787) 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, 127 + ... + 6532.

It is an arithmetic number, because the mean of its divisors is an integer number (5334660).

Almost surely, 2^21328777 is an apocalyptic number.

It is an amenable number.

21328777 is a deficient number, since it is larger than the sum of its proper divisors (9863).

21328777 is an equidigital number, since it uses as much as digits as its factorization.

21328777 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 9862.

The product of its digits is 32928, while the sum is 37.

The square root of 21328777 is about 4618.3088896262. The cubic root of 21328777 is about 277.3247634276.

The spelling of 21328777 in words is "twenty-one million, three hundred twenty-eight thousand, seven hundred seventy-seven".