21437157691 has 2 divisors, whose sum is σ = 21437157692. Its totient is φ = 21437157690.

The previous prime is 21437157689. The next prime is 21437157719. The reversal of 21437157691 is 19675173412.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 21437157691 - 2¹ = 21437157689 is a prime.

Together with 21437157689, it forms a pair of twin primes.

It is not a weakly prime, because it can be changed into another prime (21437157601) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10718578845 + 10718578846.

It is an arithmetic number, because the mean of its divisors is an integer number (10718578846).

Almost surely, 2^21437157691 is an apocalyptic number.

21437157691 is a deficient number, since it is larger than the sum of its proper divisors (1).

21437157691 is an equidigital number, since it uses as much as digits as its factorization.

21437157691 is an evil number, because the sum of its binary digits is even.

The product of its digits is 317520, while the sum is 46.

The spelling of 21437157691 in words is "twenty-one billion, four hundred thirty-seven million, one hundred fifty-seven thousand, six hundred ninety-one".