21768407 has 2 divisors, whose sum is σ = 21768408. Its totient is φ = 21768406.

The previous prime is 21768391. The next prime is 21768431. The reversal of 21768407 is 70486712.

It is a happy number.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 21768407 - 2⁴ = 21768391 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21768457) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10884203 + 10884204.

It is an arithmetic number, because the mean of its divisors is an integer number (10884204).

Almost surely, 2^21768407 is an apocalyptic number.

21768407 is a deficient number, since it is larger than the sum of its proper divisors (1).

21768407 is an equidigital number, since it uses as much as digits as its factorization.

21768407 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 18816, while the sum is 35.

The square root of 21768407 is about 4665.6625467344. The cubic root of 21768407 is about 279.2172312458.

The spelling of 21768407 in words is "twenty-one million, seven hundred sixty-eight thousand, four hundred seven".