21420676557 has 20 divisors (see below), whose sum is σ = 36570044896. Its totient is φ = 12240386280.

The previous prime is 21420676507. The next prime is 21420676579. The reversal of 21420676557 is 75567602412.

21420676557 is a `hidden beast` number, since 2 + 1 + 4 + 20 + 6 + 76 + 557 = 666.

It is not a de Polignac number, because 21420676557 - 2⁷ = 21420676429 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21420676507) by changing a digit.

It is a polite number, since it can be written in 19 ways as a sum of consecutive naturals, for example, 18888919 + ... + 18890052.

Almost surely, 2^21420676557 is an apocalyptic number.

21420676557 is a gapful number since it is divisible by the number (27) formed by its first and last digit.

It is an amenable number.

21420676557 is a deficient number, since it is larger than the sum of its proper divisors (15149368339).

21420676557 is an equidigital number, since it uses as much as digits as its factorization.

21420676557 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 37778990 (or 37778981 counting only the distinct ones).

The product of its (nonzero) digits is 705600, while the sum is 45.

The spelling of 21420676557 in words is "twenty-one billion, four hundred twenty million, six hundred seventy-six thousand, five hundred fifty-seven".