1621639440 has 100 divisors (see below), whose sum is σ = 5632216524. Its totient is φ = 432435456.

The previous prime is 1621639373. The next prime is 1621639477. The reversal of 1621639440 is 449361261.

1621639440 is a `hidden beast` number, since 16 + 2 + 1 + 639 + 4 + 4 + 0 = 666.

It can be written as a sum of positive squares in 2 ways, for example, as 252047376 + 1369592064 = 15876^2 + 37008^2 .

It is a Harshad number since it is a multiple of its sum of digits (36).

It is a junction number, because it is equal to n+sod(n) for n = 1621639395 and 1621639404.

It is an unprimeable number.

It is a polite number, since it can be written in 19 ways as a sum of consecutive naturals, for example, 118647 + ... + 131606.

Almost surely, 2^1621639440 is an apocalyptic number.

1621639440 is a gapful number since it is divisible by the number (10) formed by its first and last digit.

It is an amenable number.

1621639440 is an abundant number, since it is smaller than the sum of its proper divisors (4010577084).

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

1621639440 is a wasteful number, since it uses less digits than its factorization.

1621639440 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 250278 (or 250263 counting only the distinct ones).

The product of its (nonzero) digits is 31104, while the sum is 36.

The square root of 1621639440 is about 40269.5845521158. The cubic root of 1621639440 is about 1174.8563433848.

The spelling of 1621639440 in words is "one billion, six hundred twenty-one million, six hundred thirty-nine thousand, four hundred forty".