21253211400 has 96 divisors (see below), whose sum is σ = 66289462560. Its totient is φ = 5632727040.

The previous prime is 21253211393. The next prime is 21253211407. The reversal of 21253211400 is 411235212.

It is an interprime number because it is at equal distance from previous prime (21253211393) and next prime (21253211407).

It is not an unprimeable number, because it can be changed into a prime (21253211407) by changing a digit.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 10857 + ... + 206456.

It is an arithmetic number, because the mean of its divisors is an integer number (690515235).

Almost surely, 2^21253211400 is an apocalyptic number.

21253211400 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 21253211400, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (33144731280).

21253211400 is an abundant number, since it is smaller than the sum of its proper divisors (45036251160).

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

21253211400 is a wasteful number, since it uses less digits than its factorization.

21253211400 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 217495 (or 217486 counting only the distinct ones).

The product of its (nonzero) digits is 480, while the sum is 21.

Adding to 21253211400 its reverse (411235212), we get a palindrome (21664446612).

The spelling of 21253211400 in words is "twenty-one billion, two hundred fifty-three million, two hundred eleven thousand, four hundred".