1221240400 has 30 divisors (see below), whose sum is σ = 2934031022. Its totient is φ = 488496000.

The previous prime is 1221240343. The next prime is 1221240401. The reversal of 1221240400 is 40421221.

It can be written as a sum of positive squares in 3 ways, for example, as 21864976 + 1199375424 = 4676^2 + 34632^2 .

It is a super-2 number, since 2×1221240400² = 2982856229184320000, which contains 22 as substring.

It is a Harshad number since it is a multiple of its sum of digits (16).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1221240401) by changing a digit.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 1526151 + ... + 1526950.

Almost surely, 2^1221240400 is an apocalyptic number.

1221240400 is a gapful number since it is divisible by the number (10) formed by its first and last digit.

It is an amenable number.

1221240400 is an abundant number, since it is smaller than the sum of its proper divisors (1712790622).

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

1221240400 is a wasteful number, since it uses less digits than its factorization.

1221240400 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3053119 (or 3053108 counting only the distinct ones).

The product of its (nonzero) digits is 128, while the sum is 16.

The square root of 1221240400 is about 34946.2501564903. The cubic root of 1221240400 is about 1068.8917398051.

Adding to 1221240400 its reverse (40421221), we get a palindrome (1261661621).

The spelling of 1221240400 in words is "one billion, two hundred twenty-one million, two hundred forty thousand, four hundred".