21537667 has 2 divisors, whose sum is σ = 21537668. Its totient is φ = 21537666.

The previous prime is 21537661. The next prime is 21537671. The reversal of 21537667 is 76673512.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 21537667 - 2¹⁹ = 21013379 is a prime.

It is a zygodrome in base 9.

It is not a weakly prime, because it can be changed into another prime (21537661) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10768833 + 10768834.

It is an arithmetic number, because the mean of its divisors is an integer number (10768834).

Almost surely, 2^21537667 is an apocalyptic number.

21537667 is a deficient number, since it is larger than the sum of its proper divisors (1).

21537667 is an equidigital number, since it uses as much as digits as its factorization.

21537667 is an evil number, because the sum of its binary digits is even.

The product of its digits is 52920, while the sum is 37.

The square root of 21537667 is about 4640.8692073792. The cubic root of 21537667 is about 278.2271791713.

The spelling of 21537667 in words is "twenty-one million, five hundred thirty-seven thousand, six hundred sixty-seven".