21290551 has 2 divisors, whose sum is σ = 21290552. Its totient is φ = 21290550.

The previous prime is 21290537. The next prime is 21290567. The reversal of 21290551 is 15509212.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 21290551 - 2⁵ = 21290519 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21290501) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10645275 + 10645276.

It is an arithmetic number, because the mean of its divisors is an integer number (10645276).

Almost surely, 2^21290551 is an apocalyptic number.

21290551 is a deficient number, since it is larger than the sum of its proper divisors (1).

21290551 is an equidigital number, since it uses as much as digits as its factorization.

21290551 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 900, while the sum is 25.

The square root of 21290551 is about 4614.1685058090. The cubic root of 21290551 is about 277.1589880863.

Adding to 21290551 its reverse (15509212), we get a palindrome (36799763).

The spelling of 21290551 in words is "twenty-one million, two hundred ninety thousand, five hundred fifty-one".