1621660420 has 24 divisors (see below), whose sum is σ = 3497528664. Its totient is φ = 631132416.

The previous prime is 1621660363. The next prime is 1621660433. The reversal of 1621660420 is 240661261.

It can be written as a sum of positive squares in 4 ways, for example, as 892336384 + 729324036 = 29872^2 + 27006^2 .

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 1094977 + ... + 1096456.

It is an arithmetic number, because the mean of its divisors is an integer number (145730361).

Almost surely, 2^1621660420 is an apocalyptic number.

1621660420 is a gapful number since it is divisible by the number (10) formed by its first and last digit.

It is an amenable number.

1621660420 is an abundant number, since it is smaller than the sum of its proper divisors (1875868244).

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

1621660420 is a wasteful number, since it uses less digits than its factorization.

1621660420 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2191479 (or 2191477 counting only the distinct ones).

The product of its (nonzero) digits is 3456, while the sum is 28.

The square root of 1621660420 is about 40269.8450456418. The cubic root of 1621660420 is about 1174.8614099405.

It can be divided in two parts, 16216 and 60420, that added together give a triangular number (76636 = T₃₉₁).

The spelling of 1621660420 in words is "one billion, six hundred twenty-one million, six hundred sixty thousand, four hundred twenty".