72777781 has 2 divisors, whose sum is σ = 72777782. Its totient is φ = 72777780.

The previous prime is 72777737. The next prime is 72777827. The reversal of 72777781 is 18777727.

It is an a-pointer prime, because the next prime (72777827) can be obtained adding 72777781 to its sum of digits (46).

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 59752900 + 13024881 = 7730^2 + 3609^2 .

It is a cyclic number.

It is not a de Polignac number, because 72777781 - 2¹³ = 72769589 is a prime.

It is a super-2 number, since 2×72777781² = 10593210814567922, which contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (72777721) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 36388890 + 36388891.

It is an arithmetic number, because the mean of its divisors is an integer number (36388891).

Almost surely, 2^72777781 is an apocalyptic number.

It is an amenable number.

72777781 is a deficient number, since it is larger than the sum of its proper divisors (1).

72777781 is an equidigital number, since it uses as much as digits as its factorization.

72777781 is an evil number, because the sum of its binary digits is even.

The product of its digits is 268912, while the sum is 46.

The square root of 72777781 is about 8530.9894502338. The cubic root of 72777781 is about 417.5094116228.

The spelling of 72777781 in words is "seventy-two million, seven hundred seventy-seven thousand, seven hundred eighty-one".