21157640077 has 12 divisors (see below), whose sum is σ = 24888492540. Its totient is φ = 17931350976.

The previous prime is 21157640069. The next prime is 21157640083. The reversal of 21157640077 is 77004675112.

It is a happy number.

It can be written as a sum of positive squares in 2 ways, for example, as 13175825796 + 7981814281 = 114786^2 + 89341^2 .

It is not a de Polignac number, because 21157640077 - 2³ = 21157640069 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21157640087) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 2421418 + ... + 2430139.

It is an arithmetic number, because the mean of its divisors is an integer number (2074041045).

Almost surely, 2^21157640077 is an apocalyptic number.

It is an amenable number.

21157640077 is a deficient number, since it is larger than the sum of its proper divisors (3730852463).

21157640077 is an equidigital number, since it uses as much as digits as its factorization.

21157640077 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4851660 (or 4851653 counting only the distinct ones).

The product of its (nonzero) digits is 82320, while the sum is 40.

The spelling of 21157640077 in words is "twenty-one billion, one hundred fifty-seven million, six hundred forty thousand, seventy-seven".