21780377 has 2 divisors, whose sum is σ = 21780378. Its totient is φ = 21780376.

The previous prime is 21780361. The next prime is 21780431. The reversal of 21780377 is 77308712.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 14868736 + 6911641 = 3856^2 + 2629^2 .

It is a cyclic number.

It is not a de Polignac number, because 21780377 - 2⁴ = 21780361 is a prime.

It is not a weakly prime, because it can be changed into another prime (21780337) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10890188 + 10890189.

It is an arithmetic number, because the mean of its divisors is an integer number (10890189).

Almost surely, 2^21780377 is an apocalyptic number.

It is an amenable number.

21780377 is a deficient number, since it is larger than the sum of its proper divisors (1).

21780377 is an equidigital number, since it uses as much as digits as its factorization.

21780377 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 16464, while the sum is 35.

The square root of 21780377 is about 4666.9451464529. The cubic root of 21780377 is about 279.2684004752.

The spelling of 21780377 in words is "twenty-one million, seven hundred eighty thousand, three hundred seventy-seven".