647721984 has 264 divisors, whose sum is σ = 2169295968. Its totient is φ = 170311680.

The previous prime is 647721961. The next prime is 647722007. The reversal of 647721984 is 489127746.

It is an interprime number because it is at equal distance from previous prime (647721961) and next prime (647722007).

It is a Smith number, since the sum of its digits (48) coincides with the sum of the digits of its prime factors.

It is a Harshad number since it is a multiple of its sum of digits (48).

It is a congruent 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, 1956699 + ... + 1957029.

Almost surely, 2^647721984 is an apocalyptic number.

647721984 is a gapful number since it is divisible by the number (64) 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 647721984, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (1084647984).

647721984 is an abundant number, since it is smaller than the sum of its proper divisors (1521573984).

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

647721984 is a wasteful number, since it uses less digits than its factorization.

647721984 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 381 (or 356 counting only the distinct ones).

The product of its digits is 677376, while the sum is 48.

The square root of 647721984 is about 25450.3827869052. The cubic root of 647721984 is about 865.2259687852.

The spelling of 647721984 in words is "six hundred forty-seven million, seven hundred twenty-one thousand, nine hundred eighty-four".