21867551 has 2 divisors, whose sum is σ = 21867552. Its totient is φ = 21867550.

The previous prime is 21867541. The next prime is 21867553. The reversal of 21867551 is 15576812.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 21867551 - 2⁶ = 21867487 is a prime.

Together with 21867553, it forms a pair of twin primes.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21867553) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10933775 + 10933776.

It is an arithmetic number, because the mean of its divisors is an integer number (10933776).

Almost surely, 2^21867551 is an apocalyptic number.

21867551 is a deficient number, since it is larger than the sum of its proper divisors (1).

21867551 is an equidigital number, since it uses as much as digits as its factorization.

21867551 is an evil number, because the sum of its binary digits is even.

The product of its digits is 16800, while the sum is 35.

The square root of 21867551 is about 4676.2753340666. The cubic root of 21867551 is about 279.6404867204.

The spelling of 21867551 in words is "twenty-one million, eight hundred sixty-seven thousand, five hundred fifty-one".