21203691057 has 8 divisors (see below), whose sum is σ = 31412875680. Its totient is φ = 14135794020.

The previous prime is 21203691043. The next prime is 21203691071. The reversal of 21203691057 is 75019630212.

It is an interprime number because it is at equal distance from previous prime (21203691043) and next prime (21203691071).

It is not a de Polignac number, because 21203691057 - 2⁶ = 21203690993 is a prime.

It is not an unprimeable number, because it can be changed into a prime (21203691037) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 392660919 + ... + 392660972.

It is an arithmetic number, because the mean of its divisors is an integer number (3926609460).

Almost surely, 2^21203691057 is an apocalyptic number.

21203691057 is a gapful number since it is divisible by the number (27) formed by its first and last digit.

It is an amenable number.

21203691057 is a deficient number, since it is larger than the sum of its proper divisors (10209184623).

21203691057 is an equidigital number, since it uses as much as digits as its factorization.

21203691057 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 785321900 (or 785321894 counting only the distinct ones).

The product of its (nonzero) digits is 22680, while the sum is 36.

The spelling of 21203691057 in words is "twenty-one billion, two hundred three million, six hundred ninety-one thousand, fifty-seven".