21100431997 has 4 divisors (see below), whose sum is σ = 21100728096. Its totient is φ = 21100135900.

The previous prime is 21100431973. The next prime is 21100432021. The reversal of 21100431997 is 79913400112.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4, and also a brilliant number, because the two primes have the same length.

It is an interprime number because it is at equal distance from previous prime (21100431973) and next prime (21100432021).

It is a cyclic number.

It is not a de Polignac number, because 21100431997 - 2¹¹ = 21100429949 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 (21100434997) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 31122 + ... + 207772.

It is an arithmetic number, because the mean of its divisors is an integer number (5275182024).

Almost surely, 2^21100431997 is an apocalyptic number.

It is an amenable number.

21100431997 is a deficient number, since it is larger than the sum of its proper divisors (296099).

21100431997 is a wasteful number, since it uses less digits than its factorization.

21100431997 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 296098.

The product of its (nonzero) digits is 13608, while the sum is 37.

The spelling of 21100431997 in words is "twenty-one billion, one hundred million, four hundred thirty-one thousand, nine hundred ninety-seven".