21651480377 has 2 divisors, whose sum is σ = 21651480378. Its totient is φ = 21651480376.

The previous prime is 21651480329. The next prime is 21651480407. The reversal of 21651480377 is 77308415612.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 21586661776 + 64818601 = 146924^2 + 8051^2 .

It is a cyclic number.

It is not a de Polignac number, because 21651480377 - 2¹² = 21651476281 is a prime.

It is not a weakly prime, because it can be changed into another prime (21651483377) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10825740188 + 10825740189.

It is an arithmetic number, because the mean of its divisors is an integer number (10825740189).

Almost surely, 2^21651480377 is an apocalyptic number.

It is an amenable number.

21651480377 is a deficient number, since it is larger than the sum of its proper divisors (1).

21651480377 is an equidigital number, since it uses as much as digits as its factorization.

21651480377 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 282240, while the sum is 44.

Adding to 21651480377 its reverse (77308415612), we get a palindrome (98959895989).

The spelling of 21651480377 in words is "twenty-one billion, six hundred fifty-one million, four hundred eighty thousand, three hundred seventy-seven".