20851557420 has 96 divisors (see below), whose sum is σ = 59856572160. Its totient is φ = 5420701440.

The previous prime is 20851557401. The next prime is 20851557437. The reversal of 20851557420 is 2475515802.

It is an unprimeable number.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 1388311 + ... + 1403249.

It is an arithmetic number, because the mean of its divisors is an integer number (623505960).

Almost surely, 2^20851557420 is an apocalyptic number.

20851557420 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 20851557420, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (29928286080).

20851557420 is an abundant number, since it is smaller than the sum of its proper divisors (39005014740).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

20851557420 is a wasteful number, since it uses less digits than its factorization.

20851557420 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 15535 (or 15533 counting only the distinct ones).

The product of its (nonzero) digits is 112000, while the sum is 39.

The spelling of 20851557420 in words is "twenty billion, eight hundred fifty-one million, five hundred fifty-seven thousand, four hundred twenty".