21537029897 has 2 divisors, whose sum is σ = 21537029898. Its totient is φ = 21537029896.

The previous prime is 21537029863. The next prime is 21537029903. The reversal of 21537029897 is 79892073512.

It is a happy number.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 19717495561 + 1819534336 = 140419^2 + 42656^2 .

It is a cyclic number.

It is not a de Polignac number, because 21537029897 - 2¹² = 21537025801 is a prime.

It is not a weakly prime, because it can be changed into another prime (21537229897) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10768514948 + 10768514949.

It is an arithmetic number, because the mean of its divisors is an integer number (10768514949).

Almost surely, 2^21537029897 is an apocalyptic number.

It is an amenable number.

21537029897 is a deficient number, since it is larger than the sum of its proper divisors (1).

21537029897 is an equidigital number, since it uses as much as digits as its factorization.

21537029897 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 1905120, while the sum is 53.

The spelling of 21537029897 in words is "twenty-one billion, five hundred thirty-seven million, twenty-nine thousand, eight hundred ninety-seven".