21000647057 has 4 divisors (see below), whose sum is σ = 22616081460. Its totient is φ = 19385212656.

The previous prime is 21000647033. The next prime is 21000647069. The reversal of 21000647057 is 75074600012.

It is a Cunningham number, because it is equal to 144916²+1.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 3106501696 + 17894145361 = 55736^2 + 133769^2 .

It is a cyclic number.

It is not a de Polignac number, because 21000647057 - 2³⁰ = 19926905233 is a prime.

It is a super-2 number, since 2×21000647057² (a number of 21 digits) contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21000647557) 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, 807717182 + ... + 807717207.

It is an arithmetic number, because the mean of its divisors is an integer number (5654020365).

Almost surely, 2^21000647057 is an apocalyptic number.

It is an amenable number.

21000647057 is a deficient number, since it is larger than the sum of its proper divisors (1615434403).

21000647057 is a wasteful number, since it uses less digits than its factorization.

21000647057 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1615434402.

The product of its (nonzero) digits is 11760, while the sum is 32.

The spelling of 21000647057 in words is "twenty-one billion, six hundred forty-seven thousand, fifty-seven".