21506380373 has 2 divisors, whose sum is σ = 21506380374. Its totient is φ = 21506380372.

The previous prime is 21506380369. The next prime is 21506380453. The reversal of 21506380373 is 37308360512.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 20489918449 + 1016461924 = 143143^2 + 31882^2 .

It is a cyclic number.

It is not a de Polignac number, because 21506380373 - 2² = 21506380369 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21502380373) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10753190186 + 10753190187.

It is an arithmetic number, because the mean of its divisors is an integer number (10753190187).

Almost surely, 2^21506380373 is an apocalyptic number.

It is an amenable number.

21506380373 is a deficient number, since it is larger than the sum of its proper divisors (1).

21506380373 is an equidigital number, since it uses as much as digits as its factorization.

21506380373 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 90720, while the sum is 38.

The spelling of 21506380373 in words is "twenty-one billion, five hundred six million, three hundred eighty thousand, three hundred seventy-three".