1221042400 has 72 divisors (see below), whose sum is σ = 3110519664. Its totient is φ = 467174400.

The previous prime is 1221042373. The next prime is 1221042437. The reversal of 1221042400 is 42401221.

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

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 14781 + ... + 51580.

It is an arithmetic number, because the mean of its divisors is an integer number (43201662).

Almost surely, 2^1221042400 is an apocalyptic number.

1221042400 is a gapful number since it is divisible by the number (10) formed by its first and last digit.

It is an amenable number.

1221042400 is an abundant number, since it is smaller than the sum of its proper divisors (1889477264).

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

1221042400 is a wasteful number, since it uses less digits than its factorization.

1221042400 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 66404 (or 66391 counting only the distinct ones).

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

The square root of 1221042400 is about 34943.4171196808. The cubic root of 1221042400 is about 1068.8339701246.

Adding to 1221042400 its reverse (42401221), we get a palindrome (1263443621).

The spelling of 1221042400 in words is "one billion, two hundred twenty-one million, forty-two thousand, four hundred".