21520734537077 has 2 divisors, whose sum is σ = 21520734537078. Its totient is φ = 21520734537076.

The previous prime is 21520734536989. The next prime is 21520734537103. The reversal of 21520734537077 is 77073543702512.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 20600351415121 + 920383121956 = 4538761^2 + 959366^2 .

It is a cyclic number.

It is not a de Polignac number, because 21520734537077 - 2¹² = 21520734532981 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21520734534077) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10760367268538 + 10760367268539.

It is an arithmetic number, because the mean of its divisors is an integer number (10760367268539).

Almost surely, 2^{21520734537077} is an apocalyptic number.

It is an amenable number.

21520734537077 is a deficient number, since it is larger than the sum of its proper divisors (1).

21520734537077 is an equidigital number, since it uses as much as digits as its factorization.

21520734537077 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 8643600, while the sum is 53.

The spelling of 21520734537077 in words is "twenty-one trillion, five hundred twenty billion, seven hundred thirty-four million, five hundred thirty-seven thousand, seventy-seven".