16787921 has 2 divisors, whose sum is σ = 16787922. Its totient is φ = 16787920.

The previous prime is 16787831. The next prime is 16787923. The reversal of 16787921 is 12978761.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 11662225 + 5125696 = 3415^2 + 2264^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-16787921 is a prime.

Together with 16787923, it forms a pair of twin primes.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (16787923) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 8393960 + 8393961.

It is an arithmetic number, because the mean of its divisors is an integer number (8393961).

Almost surely, 2^16787921 is an apocalyptic number.

It is an amenable number.

16787921 is a deficient number, since it is larger than the sum of its proper divisors (1).

16787921 is an equidigital number, since it uses as much as digits as its factorization.

16787921 is an evil number, because the sum of its binary digits is even.

The product of its digits is 42336, while the sum is 41.

The square root of 16787921 is about 4097.3065543110. The cubic root of 16787921 is about 256.0544368691.

It can be divided in two parts, 167 and 87921, that added together give a palindrome (88088).

The spelling of 16787921 in words is "sixteen million, seven hundred eighty-seven thousand, nine hundred twenty-one".