21651667 has 2 divisors, whose sum is σ = 21651668. Its totient is φ = 21651666.

The previous prime is 21651607. The next prime is 21651683. The reversal of 21651667 is 76615612.

It is a happy number.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 21651667 - 2¹⁵ = 21618899 is a prime.

It is not a weakly prime, because it can be changed into another prime (21651607) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10825833 + 10825834.

It is an arithmetic number, because the mean of its divisors is an integer number (10825834).

Almost surely, 2^21651667 is an apocalyptic number.

21651667 is a deficient number, since it is larger than the sum of its proper divisors (1).

21651667 is an equidigital number, since it uses as much as digits as its factorization.

21651667 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 15120, while the sum is 34.

The square root of 21651667 is about 4653.1351796396. The cubic root of 21651667 is about 278.7172059525.

The spelling of 21651667 in words is "twenty-one million, six hundred fifty-one thousand, six hundred sixty-seven".