1021199981 has 4 divisors (see below), whose sum is σ = 1021275552. Its totient is φ = 1021124412.

The previous prime is 1021199969. The next prime is 1021199983. The reversal of 1021199981 is 1899911201.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4, and also a brilliant number, because the two primes have the same length.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-1021199981 is a prime.

It is a super-2 number, since 2×1021199981² = 2085698802388800722, which contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1021199983) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 11351 + ... + 46596.

It is an arithmetic number, because the mean of its divisors is an integer number (255318888).

Almost surely, 2^1021199981 is an apocalyptic number.

It is an amenable number.

1021199981 is a deficient number, since it is larger than the sum of its proper divisors (75571).

1021199981 is an equidigital number, since it uses as much as digits as its factorization.

1021199981 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 75570.

The product of its (nonzero) digits is 11664, while the sum is 41.

The square root of 1021199981 is about 31956.2197545329. The cubic root of 1021199981 is about 1007.0173026141.

The spelling of 1021199981 in words is "one billion, twenty-one million, one hundred ninety-nine thousand, nine hundred eighty-one".