1621172100 has 72 divisors (see below), whose sum is σ = 4714573248. Its totient is φ = 430102400.

The previous prime is 1621172099. The next prime is 1621172143. The reversal of 1621172100 is 12711261.

It is a happy number.

It is an unprimeable number.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 45385 + ... + 72815.

It is an arithmetic number, because the mean of its divisors is an integer number (65480184).

Almost surely, 2^1621172100 is an apocalyptic number.

1621172100 is a gapful number since it is divisible by the number (10) 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 1621172100, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (2357286624).

1621172100 is an abundant number, since it is smaller than the sum of its proper divisors (3093401148).

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

1621172100 is a wasteful number, since it uses less digits than its factorization.

1621172100 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 27645 (or 27638 counting only the distinct ones).

The product of its (nonzero) digits is 168, while the sum is 21.

The square root of 1621172100 is about 40263.7814915589. The cubic root of 1621172100 is about 1174.7434719900.

Adding to 1621172100 its reverse (12711261), we get a palindrome (1633883361).

The spelling of 1621172100 in words is "one billion, six hundred twenty-one million, one hundred seventy-two thousand, one hundred".