1951721940 has 144 divisors (see below), whose sum is σ = 6429326400. Its totient is φ = 441036288.

The previous prime is 1951721929. The next prime is 1951721951. The reversal of 1951721940 is 491271591.

It is an interprime number because it is at equal distance from previous prime (1951721929) and next prime (1951721951).

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 47 ways as a sum of consecutive naturals, for example, 257931 + ... + 265389.

It is an arithmetic number, because the mean of its divisors is an integer number (44648100).

Almost surely, 2^1951721940 is an apocalyptic number.

1951721940 is a gapful number since it is divisible by the number (10) 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 1951721940, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (3214663200).

1951721940 is an abundant number, since it is smaller than the sum of its proper divisors (4477604460).

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

1951721940 is a wasteful number, since it uses less digits than its factorization.

1951721940 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 7574 (or 7565 counting only the distinct ones).

The product of its (nonzero) digits is 22680, while the sum is 39.

The square root of 1951721940 is about 44178.2971604837. The cubic root of 1951721940 is about 1249.7006088310.

The spelling of 1951721940 in words is "one billion, nine hundred fifty-one million, seven hundred twenty-one thousand, nine hundred forty".