21355400820 has 48 divisors (see below), whose sum is σ = 64394749440. Its totient is φ = 5256713856.

The previous prime is 21355400819. The next prime is 21355400821. The reversal of 21355400820 is 2800455312.

It is an interprime number because it is at equal distance from previous prime (21355400819) and next prime (21355400821).

It is a Harshad number since it is a multiple of its sum of digits (30).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21355400821) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 13688580 + ... + 13690139.

It is an arithmetic number, because the mean of its divisors is an integer number (1341557280).

Almost surely, 2^21355400820 is an apocalyptic number.

21355400820 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21355400820 is an abundant number, since it is smaller than the sum of its proper divisors (43039348620).

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

21355400820 is a wasteful number, since it uses less digits than its factorization.

21355400820 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 27378744 (or 27378742 counting only the distinct ones).

The product of its (nonzero) digits is 9600, while the sum is 30.

The spelling of 21355400820 in words is "twenty-one billion, three hundred fifty-five million, four hundred thousand, eight hundred twenty".