21651277 has 2 divisors, whose sum is σ = 21651278. Its totient is φ = 21651276.

The previous prime is 21651271. The next prime is 21651281. The reversal of 21651277 is 77215612.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 19660356 + 1990921 = 4434^2 + 1411^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21651277 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21651271) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10825638 + 10825639.

It is an arithmetic number, because the mean of its divisors is an integer number (10825639).

Almost surely, 2^21651277 is an apocalyptic number.

It is an amenable number.

21651277 is a deficient number, since it is larger than the sum of its proper divisors (1).

21651277 is an equidigital number, since it uses as much as digits as its factorization.

21651277 is an evil number, because the sum of its binary digits is even.

The product of its digits is 5880, while the sum is 31.

The square root of 21651277 is about 4653.0932722223. The cubic root of 21651277 is about 278.7155324807.

Adding to 21651277 its reverse (77215612), we get a palindrome (98866889).

The spelling of 21651277 in words is "twenty-one million, six hundred fifty-one thousand, two hundred seventy-seven".