21554651 has 2 divisors, whose sum is σ = 21554652. Its totient is φ = 21554650.

The previous prime is 21554639. The next prime is 21554669. The reversal of 21554651 is 15645512.

It is a happy number.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 21554651 - 2¹⁰ = 21553627 is a prime.

It is a Sophie Germain prime.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (21554671) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10777325 + 10777326.

It is an arithmetic number, because the mean of its divisors is an integer number (10777326).

Almost surely, 2^21554651 is an apocalyptic number.

21554651 is a deficient number, since it is larger than the sum of its proper divisors (1).

21554651 is an equidigital number, since it uses as much as digits as its factorization.

21554651 is an evil number, because the sum of its binary digits is even.

The product of its digits is 6000, while the sum is 29.

The square root of 21554651 is about 4642.6986764166. The cubic root of 21554651 is about 278.3002940053.

The spelling of 21554651 in words is "twenty-one million, five hundred fifty-four thousand, six hundred fifty-one".